Taxonomy, Evolution, Pal Indicators

TAXONOMY, EVOLUTION, BIOGEOGRAPHY AND

PALAEOENVIRONMENTAL SIGNIFICANCE OF VICTORIAN PALEOGENE

OSTRACODA

Col Eglington

Department of Earth and Planetary Sciences Faculty of Science Macquarie University Sydney

This thesis is submitted to fulfil the requirements for the degree of Doctor of Philosophy from Macquarie University. All results and interpretations in this thesis are the original work of the author except where acknowledged in the customary manner. No part of this work has been submitted previously for a higher degree to any other university or institution.

Col Eglington AUGUST, 2014

Department of Earth and Planetary Sciences Faculty of Science Macquarie University Sydney ii

ABSTRACT

Section 1. The Otway Basin of southeastern Australia, which formed as part of the Australo-Antarctic Gulf during separation of Australia and Antarctica, provided a congenial marine environment for Ostracoda (Crustacea) to flourish and diversify during the Cenozoic era. Ostracod genera and species evolved rapidly and were limited ecologically by depths and temperatures. The combination of rapid rates of evolution and high ecological sensitivity makes assemblages of these morphologically complex microscopic crustaceans highly useful as biostratigraphic and especially palaeoecologic tools. Balancing evolutionary and ecologic aspects, however, requires caution in making judgements about biostratigraphic implications of specific assemblages. Their biostratigraphic value is increased when considered in conjunction with foraminiferal associations, often the principal basis for making stratigraphic alignments.

Though Cenozoic strata are widespread in western Victoria, they are generally masked by extensive Plio-Pleistocene lava sheets and are relatively rare in outcrop. Much information has been gained from the vast number of water and petroleum bores drilled through the basaltic cover into the Cenozoic sequences beneath, but relatively little of the vast amount of cores and cuttings has been subjected to palaeontologic study; none of the Paleogene intervals had previously been investigated for ostracods. The seven subsurface (from bores) and surface sections on which this study is based, are all located within the Otway Basin.

Section 2. In Latrobe-1 bore, 22 samples from a 137 m interval, ranging in age from the Paleocene–Eocene boundary to Early Eocene produced 23 taxa from nine families; two species are new: Neobuntonia taylori sp. nov. and Tasmanocypris? latrobensis sp. nov. Because of insufficient material, 14 other taxa discussed are presented in open nomenclature. The study extends the time and geographic range of most of the genera and species obtained.

Section 3. Early Eocene ostracod assemblages from the Rivernook Member of the Dilwyn Formation (Wangerrip Group) were obtained from two locations: one an outcrop, the other subsurface in Latrobe-1 bore. Samples from these sites yielded 33 taxa of which 24 were reinvestigated. Two new “dwarf” varieties, Neonesidea australis var. A and Glencoeleberis? thomsoni var. A, are proposed. Due to marked differences in faunal composition of each of the three substantial Rivernook outcrop assemblages, they could not be bulked together and treated as a single assemblage. Assemblages from the Pember Mudstone, Rivernook and Princetown members, and the Trochocyathus and Turritella beds provided data for palaeoenvironmental interpretation. Assemblage comparisons revealed a high degree of commonality between the Rivernook Member (RMA) and Pebble Point, the South Australian Late Eocene, and Late Eocene New Zealand assemblages. There was a very low degree of commonality when compared with an Eocene Antarctic assemblage. The only other bore to provide Late Paleocene/earliest Eocene ostracods, Heywood-10, had a very small latest Paleocene assemblage in the Pember Mudstone of the Dilwyn Formation. Ostracods from the Rivernook outcrop and Heywood-10 bore are the first from those locations.

Section 4. A small group of Cytherella with non-typical valve overlaps (LV>RV) is endemic to the Australian and New Zealand region. Descendants of C. atypica Bate (1972), the ancestral form from the Western Australian Late Cretaceous, migrated into the Australo- Antarctic Gulf. Cytherella postatypica sp. nov., a direct descendant, is found in the Otway Basin from the Late Paleocene to Middle Miocene. It is very similar in appearance to C. pinnata McKenzie et al. (1993), a species with a normal (RV>LV) overlap. Conspecificity was considered but rejected because of small, consistent differences in size, outline in lateral

iii view, extent of overlap, central muscle scars, and shape of juveniles. Cytherella batei sp. nov. and six taxa in open nomenclature are all new left-valve-dominant Cytherella from various Otway Basin localities that range in age from Late Eocene to Early Miocene. Inversacytherella Swanson et al. (2005), erected to accommodate Cytherella with reversed valve overlap, but otherwise morphologically very close to Cytherella postatypica and C. pinnata, and the discovery of C. conturba sp. nov., an Oligocene species in which both left- dominant and right-dominant overlaps are found, are viewed as evidence for invalidity of that supposed new genus.

Section 5. Early Eocene (Ypresian) ostracod assemblages are used for palaeoenvironmental interpretations at four locations in the northeastern part of the Australo- Antarctic Gulf. A controversial hypothesis for estimating benthic O2 levels using two ostracod groups, the platycopids and podocopids is applied to samples from bore and outcrop sections of the Pebble Point and Dilwyn formations (Wangerrip Group). In order to assess the validityt of the technique the results are compared to the foraminiferal data and presence of other ostracod taxa. It was found to concur in six instances, was contradicted in two and ambiguous in three, its veracity could not be definitively decided.

Palaeoenvironmental interpretations based on ostracod and foraminiferan assemblages are presented. There was a high degree of variability in ventilation of the substrate, despite the generally highly restricted conditions existing in this broad shelf area of the Australo- Antarctic Gulf. The environment for the Late Paleocene Pebble Point Formation outcrop assemblage was cool and well-oxygenated, deeper than the younger Rivernook Member of the Dilwyn Formation. The very small Late Paleocene Pember Mudstone (Dilwyn Formation) assemblage from Heywood-10 bore survived in a warm, shallow, poorly-oxygenated, marginal marine location. Conditions were uniformly warm and shallow for the Early Eocene Dilwyn Formation locations, but the range of estimated benthic O2 from very low to very high, and variations in composition of the assemblages, illustrate the instability of local conditions in different strata of this marginal marine setting.

Section 6. An Early Oligocene marine ostracod assemblage from the Narrawaturk Formation of the Nirranda Group occurs subsurface in the Heywood-10 bore. The sampled assemblage includes 32 taxa in 19 genera from 10 families. Two species and one subspecies are new; eight other taxa are reviewed in further detail, and eight kept in open nomenclature. The new taxa are Aversovalva hasta sp. nov., Xestoleberis heywoodensis sp. nov. and Oculocytheropteron ayressi Majoran, 1997 varius subsp. nov. The assemblage diversity was measured using the reciprocal of Simpson's Diversity Index. The Narrawaturk Formation assemblage had a lower level of diversity and abundance than the Late Oligocene Gellibrand Marl from the same locality, but a higher degree of diversity than an Early Oligocene assemblage from the Port Willunga Formation of South Australia. There was a very low level of commonality between the Narrawaturk Formation compared with the Victorian Oligocene Angahook Member. The assemblage characteristics indicate a well-ventilated inner-shelf environment with some degree of transportation. Although Australian Oligocene Ostracoda have been described from the Eocene/Oligocene boundary in South Australia, from Willunga Embayment cores, and from outcrops in the Aire and Torquay districts of southern Victoria, these specimens are the first described from the Narrawaturk Formation.

Section 7. A Late Oligocene marine ostracod assemblage from the Gellibrand Marl of the Nirranda Group occurs subsurface in the Heywood-10 bore. The sampled assemblage includes 53 taxa from 33 genera across 17 families. Twenty-five taxa were reviewed and 21 placed in open nomenclature. The diverse assemblage indicates that this inner-shelf location was slightly deeper and farther from shore than the Early Oligocene Narrawaturk Formation

iv from the same location. The water was warm, shallow and well-oxygenated. Previous Gellibrand Marl ostracod assemblages have been of Miocene age; these specimens are the first described from the subsurface Oligocene Gellibrand Marl.

Section 8. Glencoeleberis? thomsoni Hornibrook (1952), found in and above the latest Paleocene/earliest Eocene Pember Mudstone Member, Early Eocene Rivernook Member, and in Late Paleocene/Early Eocene dredged marine sediments from Fiordland in the South Island, New Zealand, provides evidence for an early breach of the Tasmanian land-bridge connecting Australia and Antarctica. Previous work suggested that breaching of the land bridge closing the eastern end of the Australo-Antarctic Gulf (that had prevented through- flow into the Tasman Sea) commenced in the mid-Late Eocene. The extension in distribution of this otherwise exclusively regional species to both sides of the Tasmanian block is evidence for a latest Paleocene/earliest Eocene breach of the barrier allowing migration from the Australo-Antarctic Gulf into the Tasman Sea. Glencoeleberis? thomsoni Hornibrook (1952), incidentally, has diagnostic features of Actinocythereis, Glencoeleberis and Trachyleberis. Its generic location is questioned because of the alignment of tubercles, the ribs beneath the rows of tubercles are sometimes very minimal, and there is thickening of the marginal pore canals. Glencoeleberis? thomsoni is morphologically diverse, including a dwarf form; both large and dwarf forms are present in Australian and New Zealand assemblages.

Section 9. A benthic marine ostracod with anomalous valve overlap, Cytherella postatypica sp. nov., found in the Late Paleocene strata of southwestern Victoria, provides evidence of an early south-flowing current down the west coast of Western Australia. Its ancestor, Cytherella atypica Bate (1972), the earliest platycopid to display left-over-right valve overlap, was endemic in the Late Cretaceous of the Carnarvon Basin of Western Australia. Presence of Cytherella postatypica in the Australo-Antarctic Gulf by the Late Paleocene is evidence of a south-flowing current that enabled the non-swimming C. atypica to migrate from the Carnarvon Basin and for its closely related descendant C. postatypica to appear in the Australo-Antarctic Gulf in and above the Late Paleocene Pebble Point Formation and Pember Mudstone of the Wangerrip Group. The southern distribution of this lineage accords with the presence of a Western Australian south-flowing current existing no later than Paleocene, much earlier than the Leeuwin Current that replaced the north-flowing West Australian Current in the Early Oligocene. This proposed current may have been near- shore, flowing counter to and inside the West Australian Current; it may have been episodic.

Section 10. In the course of research on Early Cenozoic Ostracoda (Crustacea) a method for the digital imaging and enhancement of microscopic specimens was discovered, developed and procedures established. The technique is used, in conjunction with conventional biological practices of staining, liquid emersion, transmitted light and dark field illumination, to produce highly contrasting colour images of features such as central muscle scars that are otherwise difficult to observe or SEM photograph.

NOTE REGARDING THESIS FORMAT

The thesis comprises 11 sections. Sections 2 to 10 have been written as stand-alone manuscripts formatted for publication in peer-reviewed journals. Differences between sections in text format and numbering of illustrations is due to specific formatting requirements of different journals.

Section 2 has been published (Eglington 2006). Sections 3 to 10 are to be submitted for publication shortly. All sections are solely my responsibility.

Section 10 has been prepared in a different format to the other sections due to the formatting requirements of the journal to which it is to be submitted.

Reference

EGLINGTON, C., 2006. Paleogene Ostracoda (Crustacea) from the Wangerrip Group, Latrobe-1 bore, Otway Basin, Victoria, Australia. Proceedings of the Royal Society of Victoria 118(1): 87-111.

ACKNOWLEDGEMENTS

I would first and foremost like to express my immense gratitude to my supervisors Professors John Talent and Ruth Mawson and Associate Professor Kelsie Dadd for their unfailing wisdom, support, guidance and faith over a long and arduous journey.

I would also like to thank Michael Engelbretsen for editorial input and assistance with SEMs, and Debra Birch (Department of Biological Sciences) for her on-going patience and assistance with the scanning electron microscope.

The comments and recommendations of the referees Michael Ayress, Alan Lord and Mark Warne are deeply appreciated and grateful thanks extended.

Finally, I thank all my family and friends for their support, patience and practical assistance.

TABLE OF CONTENTS

TITLE PAGE AND DISCLAIMER i ABSTRACT iii NOTE REGARDING THESIS FORMAT vi ACKNOWLEDGEMENTS vi TABLE OF CONTENTS vii LIST OF FIGURES AND PLATES xii

SECTION 1: INTRODUCTION

Structure of the thesis 1 Palaeogeographical and geologic context and location 1 Aims and methodology of the study 2 References 4

SECTION 2: PALEOGENE OSTRACODA (CRUSTACEA) FROM THE WANGERRIP GROUP, LATROBE-1 BORE, OTWAY BASIN, VICTORIA, AUSTRALIA

ABSTRACT 5 INTRODUCTION 5 PREVIOUS OSTRACOD STUDIES 5 LOCATION OF AND BACKGROUND TO THE PRESENT STUDY 6 STRATIGRAPHY 7 AGE 9 MATERIAL STUDIED 9 COMMENTS ON THE FAUNA 9 THE OSTRACOD ASSEMBLAGES 10 Pebble Point fauna 10 Rivernook fauna 10 Trochocyathus fauna 10 Princetown fauna 12 TAXONOMY 13 CONCLUSION 30 REPOSITORY 31 ACKNOWLEDGEMENTS 31 APPENDIX 31 ADDENDUM 33 REFERENCES 33

SECTION 3: NEW AND REVISED OSTRACODA (CRUSTACEA) ASSEMBLAGES FROM THE DILWYN FORMATION (LATEST PALEOCENE AND EARLY EOCENE), OTWAY BASIN, VICTORIA

ABSTRACT 39 PREVIOUS RESEARCH, BACKGROUND AND LOCATION OF PRESENT STUDY 39 GEOLOGICAL SETTING 40 Location 40 Age 41

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METHODOLOGY 41 Sampling 41 Processing 42 Images 42 Foraminiferal faunas 42 TAPHONOMY 43 Preservation 43 Contamination 43 Articulated:disarticulated 43 Adults:juveniles 43 RESULTS 43 Narrawaturk-2 and Yangery-1 bores 44 Heywood-10 bore 44 Rivernook outcrop 45 Latrobe-1 bore 45 Pebble Point fauna 45 Rivernook fauna 45 Trochocyathus fauna 46 Princetown fauna 47 Comparisons of Rivernook assemblages 47 Faunal affinities and comparisons with other studies 48 Late Paleocene Pebble Point fauna 48 South Australian Late Eocene 49 New Zealand Late Eocene 49 Antarctic Eocene 49 “Dwarf forms” 49 Palaeoenvironmental and palaeogeographic interpretations 50 TAXONOMY 50 CONCLUSION 65 REPOSITORY 65 ACKNOWLEDGEMENTS 65 APPENDIX 65 REFERENCES 67

SECTION 4: NORMAL AND INVERSE VALVE OVERLAPS BETWEEN AND WITHIN PALEOGENE CYTHERELLA (OSTRACODA) SPECIES, OTWAY BASIN, VICTORIA, AUSTRALIA

ABSTRACT 71 INTRODUCTION 71 GEOLOGICAL SETTING 72 Structural geology and location 72 Stratigraphy and age 73 METHODOLOGY 74 TAPHONOMY 74 SYSTEMATIC PALAEONTOLOGY 74 DISCUSSION 95 CONCLUSION 96 ACKNOWLEDGEMENTS 96 REFERENCES 97

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SECTION 5: CHANGING LATE PALEOCENE AND EARLY EOCENE PALAEOENVIRONMENTS NORTHEASTERN AUSTRALO- ANTARCTIC GULF USING OSTRACODA AND FORAMINIFERA

ABSTRACT 101 INTRODUCTION 101 GEOLOGICAL SETTING 102 FORAMINIFERAL FAUNAS 105 Pebble Point fauna 106 Rivernook fauna 106 Trochocyathus fauna 107 Princetown fauna 108 Palaeoenvironment 108 OSTRACODA AS INDICATORS FOR BENTHIC OXYGEN LEVELS 108 METHODOLOGY 110 RESULTS: PALAEOENVIRONMENTAL INTERPRETATIONS 111 Pebble Point fauna 111 Pebble Point Member, outcrop 111 Pember Mudstone Member, Heywood-10 bore 112 Pember Mudstone Member, Latrobe-1 bore 112 Rivernook fauna 112 Trochocyathus fauna 115 Princetown fauna 115 Diversity 116 DISCUSSION 117 The platycopid model for assessing benthic oxygen 118 Low oxygen environment of the Australo-Antarctic Gulf 118 CONCLUSION 118 ACKNOWLEDGEMENTS 119 APPENDIX 119 REFERENCES 121

SECTION 6: OSTRACODA (CRUSTACEA) OF THE NARRAWATURK FORMATION, EARLY OLIGOCENE, OTWAY BASIN, VICTORIA, AUSTRALIA

ABSTRACT 129 INTRODUCTION 129 GEOLOGICAL SETTING 130 RESULTS: THE OSTRACOD ASSEMBLAGE 131 Methodology 131 Taphonomy 131 Description 132 Discussion of the assemblage 133 Comparison with the Gellibrand Marl 133 Comparison with the South Australian Port Willunga Formation 135 Comparison with the Victorian Oligocene Angahook Member 135 Palaeoenvironment 135 TAXONOMY 135 CONCLUSION 147 REPOSITORY 147 ACKNOWLEDGEMENTS 147

REFERENCES 147

SECTION 7: OSTRACODA (CRUSTACEA) FROM THE LATE OLIGOCENE GELLIBRAND MARL, OTWAY BASIN, VICTORIA, AUSTRALIA

ABSTRACT 151 INTRODUCTION 151 GEOLOGICAL SETTING 152 METHODOLOGY 153 RESULTS 153 Composition of the ostracod assemblage 153 Comparison with other assemblages 155 Palaeoenvironmental interpretation 156 TAXONOMY 156 CONCLUSION 173 ACKNOWLEDGEMENTS 174 REFERENCES 174

SECTION 8: GLENCOELEBERIS? THOMSONI (CRUSTACEA: OSTRACODA) AS EVIDENCE FOR A LATEST PALEOCENE/EARLIEST EOCENE MARINE PASSAGE BETWEEN THE AUSTRALO-ANTARCTIC GULF AND THE TASMAN SEA

ABSTRACT 179 INTRODUCTION 179 LOCATIONS, STRATIGRAPHY AND AGES 181 RESULTS AND DISCUSSION 183 Evidence for an early marine route between the Australo-Antarctic 183 Gulf (AAG) and the Tasman Sea Latest Paleocene/earliest Eocene 183 Early Eocene 184 Middle Eocene 184 Late Eocene 185 TAXONOMY 185 CONCLUSION 191 ACKNOWLEDGEMENTS 192 REFERENCES 192

SECTION 9: THE ANOMALOUS CYTHERELLA POSTATYPICA (OSTRACODA:CRUSTACEA) AS EVIDENCE FOR A LATE PALEOCENE SOUTH-FLOWING CURRENT DOWN THE WEST COAST OF AUSTRALIA

ABSTRACT 199 INTRODUCTION 199 Palaeogeography 201 RESULTS 202 Migration pattern as evidence for an earlier West Australian 202 south-flowing coastal current CONCLUSION 203 ACKNOWLEDGEMENTS 204 REFERENCES 204

SECTION 10: ADAPTATION OF BIOLOGICAL MICROSCOPY AND DIGITAL EDITING TECHNIQUES TO MICROPALAEONTOLOGY

ABSTRACT 209 INTRODUCTION 209 METHODOLOGY 210 Conventional biological techniques applied to fossils 210 Staining. 210 Transmitted light microscopy 210 Liquid immersion with transmitted light 211 Liquid immersion with incident light 211 Equipment 211 Digital editing 211 Theory 212 Levels histogram 212 Contrast 212 Sharpening 213 Reducing loss of image data 213 Emulating biological staining with Quick Edit 213 Procedure – Photoshop Elements 214 Procedure – Photoshop CS3 215 General comments 215 ACKNOWLEDGEMENTS 215 REFERENCES 216

SECTION 11: CONCLUSION 217

Outcomes 217 New assemblages, biostratigraphy and taxonomy 217 Palaeoenvironmental interpretation 217 Palaeogeographic interpretation 218 Additional results 218

FIGURES, PLATES AND TABLES

SECTION 2: PALEOGENE OSTRACODA (CRUSTACEA) FROM THE WANGERRIP GROUP, LATROBE-1 BORE, OTWAY BASIN, VICTORIA, AUSTRALIA

Fig. 1. Site of the Latrobe-1 borehole near Princetown and neighbouring 7 locations of Rivernook and Pebble Point, Otway Basin, Victoria. Table 1. Distribution of early Paleogene Ostracoda, chronostratigraphy 11 and faunal units in Latrobe-1 borehole. Table 2. Breakdown of distribution of species in Latrobe-1 bore from samples 12 aggregated in Table 1.

Fig. 2. A-F. Cytherella pinnata McKenzie, Reyment & Reyment 1993. A. ACLV, 16 P312750. B. AFRV internal, P312751. C. Detail of margin, RV internal, P312751. D. Detail of margin, LV internal, P312752. E. Juv. RV external, P312753. F. AFLV internal, P312752. G-N. Cytherella sp. cf. C. atypica Bate 1972. G. AFRV internal, P312757. H. AMLV internal, P312758. I. Adductor muscle scars, RV internal, P312757. J. Juv. RV external, P312755. K. ARV external, P312756. L. AFCRV, P312759. M. Details of margin, LV internal, P312758. N. Details of margin, RV internal, P312757. O. Cytherella sp., AFLV, P312754. P. Cytherella sp. cf. C. atypica Bate 1972, details of margin LV internal, P312758. Q. Cytherelloidea praeauricula (Chapman 1926), AFRV, P312763. R. Xestoleberis? sp. CLV external, P312760.

Fig. 3. A-B. Cytherelloidea jugifera McKenzie, Reyment & Reyment 1991. 20 A. ACRV, P312762. B. Juv. LV, P312761. C-D. Cytherelloidea hrycga? McKenzie, Reyment & Reyment 1993.C. Detail of adductor muscle scars external. D. Juv. LV external, P312790. E-F. Paracypris sp. E. Damaged LV internal, P312767. F. LV internal adductor muscle scars, P312767. G-I. Tasmanocypris? latrobensis sp. nov. G. ARV external, P312764. H. ALV external, P312765. I. ALV internal, P312766. J-K. Tasmanocypris? sp. J. LV internal, P312769. K. CRV external, P312768. L-M. Neonesidea aff. N. australis (Chapman 1914). L. ACLV, P312770. M. ARV internal, P312771. N. Cytheralison corrugata? fragment RV, external, P312775. O. Cytheralison sp. fragment LV, P312778. P. Kuiperiana sp. cf. K. lindsayi (McKenzie, Reyment & Reyment 1991) ACLV, P312773.

Fig. 4. A. Loxoconcha sp. P312772 damaged LV. B-E. Neobuntonia taylori sp. nov. 24 B. Holotype, RV external detail of “hinge ear” area, P312774. C. Paratype RV internal detail anterior hinge element and possible ocular sinus, P312777. D. Holotype ARV external, P312774. E. Paratype ARV internal, P312777. F. Echinocythereis karooma McKenzie, Reyment & Reyment 1993, AMRV, P312779. G. Cletocythereis kurrawa McKenzie, Reyment & Reyment 1993, ACLV, P312781. H. Munseyella dunoona McKenzie, Reyment & Reyment 1993, ACRV, external, P312780. I. Echinocythereis karooma McKenzie, Reyment & Reyment 1993, AFRV, P312776. J. Trachyleberis thomsoni AMRV internal, P312787. K, Indet. gen. sp. fragment RV, P312782. L-M. Trachyleberis thomsoni? small form. L. AFLV external, P312784. M. AMRV external, P312785. N. Trachyleberis thomsoni damaged juv. LV external, P312788. O. Trachyleberis? sp. adult LV external, P312783. P-Q. T. thomsoni large form. P. ALV external, P312789. Q. ALV external, P312786.

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Fig. 5. A-J. Neobuntonia taylori Eglington 2006. 28 A, D. Holotype LV (P312791) and RV (P312774) lateral views. B. Holotype carapace dorsal view prior to opening (valves P312774 and P312791). C. Holotype C ventral view prior to opening (valves P312774 and P312791). E. Holotype, anterior hinge element and optic sinus, RV internal view, P312774. F. Holotype, LV and RV hinge elements, valves P312791 and P312774. G. Central muscle scars. H. Holotype LV posteral view P312791. I. Holotype RV posteral view P312774. J. RVs posteral views. K. Neobuntonia batesfordiense (Chapman 1910) posterior view. L-M. Tasmanocypris? sp. P312769. L. Adductor muscle scars. M. LV internal view.

Appendix 1. Stratigraphy, biostratigraphy and sampling data, Latrobe-1, Otway 32 Basin, Victoria.

SECTION 3: NEW AND REVISED OSTRACODA (CRUSTACEA) ASSEMBLAGES FROM THE DILWYN FORMATION (LATEST PALEOCENE AND EARLY EOCENE), OTWAY BASIN, VICTORIA

Fig. 1. Key locations within the Otway Basin, Victoria. 40 Fig. 2. Rivernook, Pebble Point and Latrobe-1 borehole, Princetown Area, 41 Otway Basin, Victoria. Table 1. Earliest Early Eocene ostracod assemblages from outcropping 44 Rivernook Member, Dilwyn Formation, Otway Basin, Victoria. Table 2. Ostracod assemblages for Pebble Point and Rivernook faunas, Latrobe-1, 46 Otway Basin, Victoria. Table 3. Ostracod assemblages for Princetown and Trochocyathus faunas, 47 Latrobe-1, Otway Basin, Victoria. Table 4. Rivernook Member outcrop and Latrobe-1 bore ostracod assemblages. 48

Plate 1. A. Cytherella postatypica, AMLV int. B. Tasmanocypris? latrobensis, 52 ALV int. C. Cytherelloidea jugifera, AMCRV. D. Tasmanocypris sp. 2, LV int. E. Paracypris sp. 1, ALV int. damaged. F. Tasmanocypris sp. cf. T. eurylamella, adult RV int. G. Neonesidea australis var. A, LV. H-I. Pseudeucythere pseudosubovalis. H. CLV. I. CRV. J, L-M. Rotundracythere sp. aff. R. rotundra, adult. J. LV internal. L. RV ext. from same individual. M. Ornament detail of RV. K. Tasmanocypris sp.1, adult LV int. N-O. Eucythere? sp., CRV. N. SEM. O. Light microscope digital photo of same specimen to show ornament.

Plate 2. A. Munseyella kleithria Neil 1997, adult CLV. B, E. Munseyella 58 bungoona McKenzie, Reyment & Reyment 1993, C adult LV, CRV. C. Munseyella adaluma McKenzie, Reyment & Reyment 1993, CLV. D. Munseyella dunoona McKenzie, Reyment & Reyment 1993, adult CRV. F. Incertae sedis, damaged LV. G-H. “Cythereis” sp., adult RV ext. and int. same specimen. I. Oertliella? sp., adult CLV. J. Oertliella? sp., juv. damaged LV. K. “Hermanites” lungalata (McKenzie, Reyment & Reyment 1993), juv. LV. L. Trachyleberis brevicosta major McKenzie, Reyment & Reyment 1991, adult CRV. M. Trachyleberis reticulopustulosa?, adult RV. N. Glencoeleberis? thomsoni thomsoni large, adult male RV. O. Glencoeleberis? thomsoni thomsoni var. A, adult RV. P. Trachyleberis? sp. CLV. Q. T. thomsoni var. A, adult RV. R. Echinocythereis sp., CLV.

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Plate 3. A. Scepticocythereis sanctivincentis Majoran (1996), C dorsal view 62 (after Majoran 1996). B. “Cythereis” sp., RV dorsal view. C. Paracypris sp. RV external view. D. Rotundracythere aff. R. rotunda, RV internal view. E-I. Anterior hinge elements area, RVs internal views, (OS = optic sinus; IM = inner margin). E-F. Scepticocythereis sanctivincentis, South Australia, Eocene. G-H. Scepticocythereis sp. Browns Creek Clays, Castle Cove and Browns Creek, Victoria, Late Eocene. I. “Cythereis”sp., Rivernook Member outcrop.

Appendix 1. Stratigraphy, biostratigraphy and sampling data, Latrobe-1, 65 Otway Basin, Victoria. Appendix 2. Otway Basin stratigraphy for the study area. 66

SECTION 4: NORMAL AND INVERSE VALVE OVERLAPS BETWEEN AND WITHIN PALEOGENE CYTHERELLA (OSTRACODA) SPECIES, OTWAY BASIN, VICTORIA, AUSTRALIA

Fig. 1. Locations, Otway Basin, Victoria, Australia. 72 Fig. 2. Bells Headland and Point Addis Beach, southeastern Victoria, Australia. 73

Plate 1. A-I. Cytherella pinnata. 80 A. FRV, Browns Creek Clays, Browns Creek. B. MRV, Browns Creek Clays, Browns Creek. C. FC, dorsal, Browns Creek Clays, Browns Creek. D. FLV, Browns Creek Clays, Browns Creek. E. MLV, Browns Creek Clays, Browns Creek. F. MLV, Browns Creek Clays, Browns Creek. G. FLV internal, Rivernook Member, Latrobe-1, 295.96 m. H. MCLV, Rivernook Member, Latrobe-1, 295.96 m. I. FRV internal, Turritella Bed, Latrobe-1, 262.7 m. J-O. Cytherella postatypica, Latrobe-1. J. C. Paratype dorsal, Princetown Member, Latrobe-1, 229.21 m. K. Paratype FRV, Dilwyn Formation, Latrobe-1, 260.6 m. L. Paratype MLV, Rivernook Member, Latrobe-1, 295.35 m. M. Holotype FRV internal, Dilwyn Formation, Latrobe-1, 260.6 m. N. Paratype MLV internal, Rivernook Member, Latrobe-1, 295.35 m. O. Paratype FCRV, Princetown Member, Latrobe-1, 229.21 m.

Plate 2. A-C. Cytherella atypica Toolonga Calcilutite, Carnarvon Basin, Western 84 Australia, Late Cretaceous. A. Paratype Io 4370 FRV. B. Paratype Io 4371 FLV internal. C. Paratype Io 4374 MC dorsal. D-I. Cytherella batei sp. nov. D. Paratype FCRV, Clifton Formation, Narrawaturk-2. E. Paratype FCLV, Gellibrand Marl, Heywood-10. F. Paratype MRV, Gellibrand Marl, Heywood-10. G. Holotype, FLV, Gellibrand Marl, Narrawaturk-2, 522-526 m. H. Paratype MC dorsal, Gellibrand Marl, Heywood-10. I. Paratype FLV, Clifton Formation, Narrawaturk-2. J. Cytherella postatypica paratype FCLV, Pember Mudstone Member, Heywood-10. K. Cytherella batei sp. nov. paratype FC dorsal, Gellibrand Marl, Narrawaturk-2. L-M. Cytherella sp. cf. C. batei, Yangery-1. L. MLV, Narrawaturk Marl, Yangery-1. M. MRV, Narrawaturk Marl, Yangery-1. N-O. Cytherella aff. batei, Heywood-10. N. MLV, Gellibrand Marl, Heywood-10. O. FRV, Gellibrand Marl, Heywood-10. P. Cytherella postatypica paratype P312755 JRV, Rivernook Member, Latrobe-1, 295.35 m. Q. Cytherella pinnata paratype P312753 JRV Turritella Bed, Latrobe-1, 264.6 m.

Plate 3. A. Cytherella sp. aff. C. postatypica sp. 1, FRV, Gellibrand Marl, 86

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Yangery-1. B. Cytherella sp. aff. C. postatypica sp. 2, CRV, Narrawaturk Formation, Yangery-1. C-D. Cytherella sp. aff. C. postatypica sp. 3, Browns Creek Clays, Castle Cove. C. FRV. D. MRV. E-R. Cytherella conturba sp. nov. E-K. Bells Headland, Addis Beach. E. Paratype, FCRV. F. Paratype, FCLV. G. Holotype, FC dorsal. H. Paratype, FC dorsal. I. Paratype, FC juv. dorsal. J. Paratype, FC juv. dorsal. K. Paratype, MC juv. dorsal. L. Paratype, JCFLV external. M. Paratype, JFLV internal. N. Paratype, JFRV external. O. Paratype, JLV external. P. Paratype, AMRV internal, Bells Headland Addis Beach. Q-R. Paratype, detail of Fig. P margin. S. C. sp. cf. C. conturba MRV length 0.82 mm, Narrawaturk Marl, Yangery-1, ~503m. L-O. Location “Upper bed of marine clays west of Bells Headland (Carter 4)”.

Plate 4. A-C. Cytherella pinnata, RV, CMS, Browns Creek Clays, Browns Ck. 90 D-E. Cytherella sp. cf. C. atypica sp. 5. RV damaged postero-dorsal margin & CMS, Browns Creek Clays, Browns Creek. F-I. Cytherella postatypica. F. Paratype CMS, Browns Creek Clays, Browns Creek. G-I. Paratype RV juv, CMS, Browns Creek Clays, Browns Creek. J. Cytherella sp. aff. C. postatypica sp. 4, FRV dorsal, Castle Cove. K-P. Cytherella batei sp. nov. K. Paratype MCLV, Gellibrand Marl, Heywood-10. L. Holotype, FLV, Gellibrand Marl, Narrawaturk-2, 466-467 m. M. Paratype FC dorsal, Narrawaturk-2. N. Holotype CMS. O. Paratype FLV dorsal, Narrawaturk-2. P. Paratype FLV dorsal, Narrawaturk-2. Q-U. Cytherella conturba sp. nov. Q. Paratype AMRV. R. Holotype FCLV. S. Holotype FC dorsal. T. Paratype FC dorsal. U. AMRV dorsal.

Fig. 3. Range and distribution of sinistral Cytherella. 96

SECTION 5: CHANGING LATE PALEOCENE AND EARLY EOCENE PALAEOENVIRONMENTS NORTHEASTERN AUSTRALO- ANTARCTIC GULF USING OSTRACODA AND FORAMINIFERA

Fig. 1. Bore locations and relevant structural features, Otway Basin, Victoria. 103 Fig. 2. Rivernook Member locations (Rivernook and Latrobe-1) near Princetown, 104 Otway Basin, Victoria. Table 1. Pebble Point, Rivernook-A, Rivernook and Princetown ingressions, 105 Otway Basin, Victoria. Table 2. Platycopid percentages and derived O2 levels in samples from the Rivernook 113 fauna. Table 3. Platycopid percentages and derived O2 levels in Latrobe-1 Trochocyathus 115 fauna. Table 4. Platycopid percentages and derived O2 levels in Latrobe-1 bore Princetown 116 fauna. Table 5. Diversity of the ostracod assemblages from Latrobe-1 borehole and 117 RivernookMember outcrop using the reciprocal of Simpson's Diversity Index, higher number = greater diversity. Assemblages of < 8 specimens have not been included, * are considered to be too small for discussion. Appendix. Sample positions, platycopid percentages and O2 levels in Latrobe-1 bore 120 and outcropping Rivernook Member, Early Eocene, Otway Basin, Victoria.

SECTION 6: OSTRACODA (CRUSTACEA) OF THE NARRAWATURK FORMATION, EARLY OLIGOCENE, OTWAY BASIN, VICTORIA, AUSTRALIA

Fig. 1. Location of Heywood-10 bore, Otway Basin, Victoria, Australia. 130 Table 1. Heywood-10 Eocene–Oligocene stratigraphy and biostratigraphy. 131 Fig. 2. Abundance in ostracod families for Narrawaturk Formation, Heywood-10 132 bore, Otway Basin, southern Victoria. Figures are actual numbers of specimens. Fig. 3. Composition of the ostracod assemblage, abundance within species and 132 subspecies for Early Oligocene Narrawaturk Formation, Heywood-10 bore. Fig. 4. Comparison of abundance in families of ostracods from the Early Oligocene 134 Narrawaturk Formation and Late Oligocene Gellibrand Marl, Heywood-10 bore, Otway Basin, Victoria. Fig. 5. Comparison of abundance of specimens in Gellibrand Marl and Narrawaturk 134 Formation.

Plate 1. A. Neonesidea australis (Chapman, 1914), CRV. 136 B-F. Paranesidea? sp. B. CRV. C-E. LV internal; detail. F. Detail of surface of Fig. B. G. Argilloecia sp. aff. A. allungata McKenzie, Reyment & Reyment, 1993, CLV. H. Cardobairdia balcombensis Whatley & Downing 1983, CRV. I-J. Xestoleberis basiplana McKenzie, Reyment & Reyment, 1993. I. CRV. J. C dorsal. K-O. Xestoleberis heywoodensis sp. nov. K. C dorsal. L. CLV. M. CRV. N. LV internal. O. LV hinge detail. P-R. Munseyella adaluma McKenzie, Reyment & Reyment, 1993. P-Q. CLV. R. C dorsal. S. Propontocypris sp. CLV.

Plate 2. A. Munseyella splendida Whatley & Downing, 1983, CRV. 142 B. Munseyella warringa? McKenzie, Reyment & Reyment, 1993, CRV. C. Kangarina wareelacoggorra McKenzie, Reyment & Reyment, 1993, CRV. D. Hemiparacytheridea sp. CRV. E. Eucytherura delta CRV. F-H. Oculocytheropteron ayressi varius sub. sp. nov. F. C dorsal. G. CRV. H. C dorsal. I-K. Oculocytheropteron microfornix Whatley & Downing, 1983. I. C dorsal. J. CRV.K. CLV. M-P. Aversovalva yaringa yaringa McKenzie, Reyment & Reyment, 1993. M. CLV. N. CRV. O. C anterior. P. C dorsal.

Plate 3. A-B. Hemicytherura fulva McKenzie, Reyment & Reyment, 1993, 144 CLV. C-E. Aversovalva yaringa minor McKenzie, Reyment & Reyment, 1993. C. C dorsal. D. CLV. E. CRV. F-K. Aversovalva hasta sp. nov. F. RV. G. LV. H. C dorsal. I. C anterior. J. LV int. K. CRV. L. Cytherelloidea marginopytta McKenzie, Reyment & Reyment, 1991, FCLV. M. Alataleberis johannae McKenzie & Warne 1986, CLV. N. Bradleya regularis McKenzie, Reyment & Reyment, 1991, RV juv. O. Bradleya (Quasibradleya) janjukiana McKenzie, Reyment & Reyment, 1991, LV.

SECTION 7: OSTRACODA (CRUSTACEA) FROM THE LATE OLIGOCENE GELLIBRAND MARL, OTWAY BASIN, VICTORIA, AUSTRALIA

Fig. 1. Location of the Heywood-10 bore, Otway Basin, Victoria, Australia. 152 Table. 1. Heywood-10 bore Oligocene–Miocene stratigraphy and biostratigraphy. 153 Fig. 2. Abundance in families, Gellibrand Marl, Heywood-10 bore, 154 Otway Basin, southern Victoria.

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Table 2. The composition of the ostracod assemblage 155

Plate 1. A-B. Cytherella sp. A. FRV. B. FRV. 158 C-E. Cytherella sp. aff. C. paranitida Whatley & Downing, 1983, FCRV. C. FCRV. D. Detail posterior surface. E. Detail anterior surface. F-G. Cytherella sp. aff. C. batei. F. FRV. G. MLV. H. Cytherelloidea intermedia (Chapman, Crespin & Keeble, 1928), MC dorsal. I. Platella parapunctata (Whatley & Downing, 1983), CFRV. J. Cytherelloidea jugifera McKenzie, Reyment & Reyment, 1991, RV. K. Cytherelloidea intermedia (Chapman, Crespin & Keeble, 1928), FRV. L. Cytherelloidea jugifera McKenzie, Reyment & Reyment, 1991, RV. M. Cardobairdia? sp. CRV. N. Paracypris sp. CRV. O. Paracypris sp. aff. P. bradyi McKenzie, 1967, CRV. P-Q. Tasmanocypris? sp. CRV. R. Argilloecia sp. aff. A. allungata McKenzie, Reyment & Reyment, 1993, CLV. S. Sclerochilus sp. T. Propontocypris? sp. CLV.

Plate 2. A-B. Loxoconcha mcgowrani McKenzie, Reyment & Reyment, 1991. 164 A. FCRV. B. MCRV. C-D. Loxoconcha punctabella McKenzie, Reyment & Reyment, 1991. C. FCRV. D. MCLV. E. Saida sp. aff. S. daisa McKenzie, Reyment & Reyment, 1993, LV. F. Munseyella splendida Whatley & Downing, 1983, CLV. G-H. Munseyella adaluma McKenzie, Reyment & Reyment, 1993. G. CRV. H. CLV. I. Munseyella splendida Whatley & Downing, 1983, CRV. J. Rockallia sp. CRV. K. Kangarina wareelacogorra McKenzie, Reyment & Reyment, 1993, CRV. L. Eucytherura cameloides McKenzie, Reyment & Reyment, 1993, CLV. M-N. Hemiparacytheridea sp. Detail and CLV. O. Eucytherura horrida McKenzie, Reyment & Reyment, 1993, CLV. P. Hemiparacytheridea sp. C dorsal. Q. Eucytherura cameloides McKenzie, Reyment & Reyment, 1993, C dorsal. R. Eucytherura horrida McKenzie, Reyment & Reyment, 1993, C dorsal.

Plate 3. A-C. Oculocytheropteron microfornix Whatley & Downing, 1983. 166 A. CRV. B. dorsal. C. CRV. D. Cytheropteron sp. aff. C. ruwarungensis Majoran, 1997, CRV. E-F. Oculocytheropteron ayressi varius subsp. nov. E. CLV. F. C dorsal. G-J. Aversovalva yarringa yarringa McKenzie, Reyment & Reyment, 1993. G-H. CRV. I. C dorsal. J. CLV. K. Pseudeucythere? sp. CRV. L. Indet. gen. sp. 2 CLV. M. Pseudeucythere pseudosubovalis (Whatley & Downing, 1983), CLV. N. Indet. gen. sp. 1 CRV. O. Bidgeecythere sp. CLV. P. Orlovibairdia sp. CRV. Q. Uroleberis minutissima (Chapman, Crespin & Keeble, 1926), CRV.

Plate 4. A. Bradleya (Quasibradleya) momitea McKenzie, Reyment & Reyment, 170 1993, CRV. B. Bradleya sp. cf. B. regularis McKenzie, Reyment & Reyment, 1991, CRV. C. Trachyleberis brevicosta major McKenzie, Reyment & Reyment, 1991, CRV. D-E. Glencoeleberis? sp. aff. G?. thomsoni. D. Surface detail. E. MLV. F. Cytheropteron sp. aff. C. ruwarungensis Majoran, 1997, C dorsal outline traced from digital optical photo. G-H. Cytherelloidea marginopytta McKenzie, Reyment & Reyment, 1991. G. Detail of second, third and fourth orders of ornament. H. FCRV.

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SECTION 8: GLENCOELEBERIS? THOMSONI (CRUSTACEA: OSTRACODA) AS EVIDENCE FOR A LATEST PALEOCENE/EARLIEST EOCENE MARINE PASSAGE BETWEEN THE AUSTRALO-ANTARCTIC GULF AND THE TASMAN SEA

Fig. 1. Tectonic and oceanographic reconstructions of the Australo-Antarctic Gulf 180 (AAG) and Tasman Sea regions, Early Eocene, arrows indicate the main current flow. Fig. 2. Locations and structures within the Otway Basin, Victoria, Australia. 181 Fig. 3. Latrobe-1 and Rivernook locations, Otway Basin, southern Victoria. 182 Fig. 4. Browns Creek and Castle Cove locations, Otway Basin, southern Victoria. 182 Table 1. Castle Cove stratigraphy. 182 Table 2. Australian and New Zealand locations or strata referred to from 183 published papers.

Plate 1. A-D. Trachyleberis careyi McKenzie, Reyment & Reyment (1991). 190 A. MRV (from McKenzie et al. 1991, Plate 7, fig. 11), L= ~ 0.93 mm. B. FRV (from McKenzie et al. 1991, Plate 7, fig. 12), L= ~ 0.9 mm. C. MLV, Browns Creek Clays, Castle Cove. D. FRV, Browns Creek Clays, Castle Cove. E. Glencoeleberis? thomsoni, (non T. cf. careyi from McKenzie et al. 1993, Plate 6, fig. 6), MLV, L=0.89 mm, H=0.46 mm. F. G.? thomsoni var. A, FRV (Section 3, Plate 2, fig. Q herein), Rivernook Member, Rivernook. G. G.? thomsoni large form, LVM, L=1.1 mm. H = 0.56 mm., Browns Creek Clays, Castle Cove. H. G?. thomsoni, LV, L=1.0 mm (from Majoran, 1996a, Fig. 9L). I. G?. thomsoni (Hornibrook 1952), from Hornibrook, 1952, Plate 3, fig. 40), RV, L = 1.3 mm. J. G.? thomsoni var. A, adult LV (Section 3, Plate 2, fig. N herein), FLV, Trochocyathus Bed, Dilwyn Formation, Latrobe-1 bore. K. G?. thomsoni, MLV, L=1.28 mm (from Ayress, 1993a, Fig. 9Q). L. G.? cf. occultata Jellinek & Swanson (2003), MLV, L=1.25 mm (previously Trachyleberis thomsoni robust form, from Ayress, 1993a, Fig. 9R). M. G.? thomsoni var. A, FRV, (Section 3 herein), Rivernook Member, Rivernook. N. G.? thomsoni?, FLV, Browns Creek Clays, Castle Cove. O. G?. thomsoni (Hornibrook 1952), from Hornibrook, 1952, Plate 3, fig. 47), L=1.26 mm. P. G.? thomsoni var. A, RV dorsal, Princetown Member, Latrobe-1. Q. G.? thomsoni, large form, inner marginal zone, RV anterior, Browns Creek Clays, Castle Cove. R. G?. thomsoni small form (from Ayress 1995, Fig. 11.5), MRV. S. Actinocythereis tetrica (Brady 1880; from McKenzie & Pickett 1984, Fig. 4CC), MRV. T. G?.? thomsoni var. A, inner marginal zone, LV anterior, Rivernook Member, Rivernook. U. G.? thomsoni large form, inner marginal zone, LV anterior, Browns Creek Clays, Castle Cove. V. ?Actinocythereis sp. A, (from Neil 1994, Plate 1, fig. 4), ALV. W. A. tetrica (Brady 1880; from McKenzie & Pickett 1984, Fig. 4EE), FLV.

SECTION 9: THE ANOMALOUS CYTHERELLA POSTATYPICA (OSTRACODA:CRUSTACEA) AS EVIDENCE FOR A LATE PALEOCENE SOUTH-FLOWING CURRENT DOWN THE WEST COAST OF AUSTRALIA

Fig. 1. Locations and structures, Otway Basin, Victoria, Australia. 200 Fig. 2. Outcrop and bore locations in the Princetown area, Victoria. 200 Fig. 3. Paleocene–Eocene range and distribution of Cytherella atypica Bate (1972), 202 C. postatypica sp. nov. and related sinistral Cytherellas.

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Fig. 4. Tectonic and oceanographic reconstructions of the Australo-Antarctic Gulf 203 (AAG) and Carnarvon Basin location, Early Eocene. Block arrow indicates the direction of the proposed Paleocene current flowing south along the West Australian coast. Narrow arrows indicate the main current flow in the Early Eocene AAG (adapted from McGowran et al. 1997b; Cande & Stock 2004; Exon, Kennett & Malone 2004d); OB = Otway Basin.

SECTION 10: ADAPTATION OF BIOLOGICAL MICROSCOPY AND DIGITAL EDITING TECHNIQUES TO MICROPALAEONTOLOGY

Fig. 1. Small untreated translucent Early Tertiary Callistocythere carapace (left) under 210 incident light. Same species, (different specimen) viewed simultaneously with incident and transmitted light has been stained with methylene blue (middle), then digitally enhanced (right). Fig. 2. Photoshop Levels histogram of an unedited ostracod carapace SCAN 212 (Cytherella pinnata McKenzie, Reyment & Reyment, 1993) showing most of data in the darker region of the chart towards the 0/left end. The mid-range tapers off into the lighter values with no white present (255/far right). Fig. 3. The image has been Levels-adjusted for better contrast, the histogram appears 212 spiky with gaps due to it now being spread over the full range 0–255 once the left and right ends were removed, but little data have been lost. Fig. 4. The image has been over-adjusted, it now has white/highlights and black areas 212 from which all data have been lost, the histogram is crammed (clipped) against the 0 (left) and 255 (right) ends of the graph rather than displaying the tails tapering off as in Fig. 3. Fig. 5. The image (top), cropped from Fig. 3, has then been sharpened (bottom) 213 resulting in loss of peaks/data as shown in its histogram. The single bars at 0 (left) and 255 (right) represent the areas of pure black and pure white, they are significantly higher than previously, indicating the extent to which differentiation resulting from sharpening has pushed values into these two zones. Fig. 6. A small, left valve internal view of a transparent Early Tertiary ostracod 214 Argilloecia (left) has been digitally enhanced (middle) then the central muscle scars (CMS ) area cropped (right) and further developed using Levels – Auto button in Quick Edit. Fig. 7. Valve of an Early Tertiary Glencoeleberis? thomsoni (Ostracoda) immersed in 215 water and viewed under biological microscope using transmitted light reflected from the sky (left). Image then cropped and enlarged to view anterior marginal zone (middle) then edited (right) as described (steps 2, 4, 6, 7). Fig. 8. Marginal pore canals from a Recent paracyprid shell fragment (left) before 215 (middle) and after digital enhancement (right).

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SECTION 1

INTRODUCTION

Structure of the thesis

The thesis has been written as 11 sections, eight are intended for publication as separate papers (Sections 3–10), the ninth (Section 2) has been published (Eglington 2006). The formatting and layout of Section 10 is different from the other sections due to the requirements of the journal to which it will be submitted for publication.

Palaeogeographical and geologic context and location

During the Late Cretaceous the separation of the Australian and Antarctic continental blocks created the Australo-Antarctic Gulf (AAG), a long, narrow, east-west oriented sea, open only at the western end (Exon et al. 2004b). Initially shallow and warm, with limited circulation, the Gulf gradually deepened and widened as separation of the continental blocks continued (Exon et al. 2004b). The Tasmanian land bridge, at 70°–65°S, effectively blocked the eastern end of the Gulf, prohibiting any significant through-flow into the developing Tasman Sea until the latest Eocene/earliest Oligocene (Exon et al. 2004a, 2004b).

Changes in climatic conditions were very significant through the Paleogene, commencing with the warm "Greenhouse" climate in the Cretaceous, climaxing at the Paleocene-Eocene thermal maximum, tapering off through to the cold episode at the beginning of the Oligocene, followed by the variable climate of the Oligocene (Exon et al. 2004a). The water temperature in the AAG during the Eocene was warmer than the southern Proto-Pacific Ocean (Exon et al. 2004b).

The locations sampled for this research are all within the Victorian portion of the Otway Basin. The Otway Basin is approximately 500 km long, extends both on and off shore, and is one of a series of east-west-trending rift basins formed along the northern edge of the AAG by the Gondwana break-up (Duddy 2003). The Bureau of Mineral Resources first used the term Otway Basin in 1958 to describe the coastal strip between Nelson and Port Phillip Bay. By 1960 the definition was extended to include the currently accepted limits, a trough-like depression running east-west between Lacepede Bay, South Australia and the eastern side of Port Phillip Bay, Victoria (Wopfner & Douglas 1971a). The northern limit is defined by the major steepening of the gravity gradient at the northern edge of the thick Lower Cretaceous/Cenozoic sedimentary rocks, and the eastern limit at the Mornington Peninsula– King Island Basement Ridge. The southern limit is offshore and inferred from seismic interpretation (Wopfner & Douglas 1971a). The main structural components of the Victorian onshore area of the basin are the Warrnambool and Otway Ranges Highs, and the Port Campbell and Tyrendarra Embayments (Wopfner & Douglas 1971a). The basin contains thick Mesozoic and Cenozoic strata ( Abele et al. 1993; Holdgate & Gallagher 2003).

The main sedimentary stratigraphic units within the portion of the Otway Basin in which sampling took place, are the Wangerrip Group which consists of the Pebble Point Formation of Paleocene age, and the Dilwyn Formation of Middle Paleocene–Early Eocene age. The Wangerrip Group is overlain by the Nirranda Group of Late Eocene–Early Oligocene age containing the Mepunga and Narrawaturk Formations. The Nirranda Group is overlain by the Heytesbury Group of Late Oligocene–Late Miocene age which here consists of the Clifton Formation, the Gellibrand Marl and the Port Campbell Limestone Holdgate & Gallagher 2003).

During the Paleogene the locations were situated in the north-eastern AAG along a wide, shallow shelf, neritic to marginal marine with highly restricted circulation (Holdgate & Gallagher 2003; Exon et al. 2004b).

Aims and methodology of the study

Although outcrops of Paleogene sedimentary rock in the Otway Basin are limited, there has been extensive on- and offshore exploratory drilling for over 100 years (Wopfner & Douglas 1971b; Bernecker et al. 2003). The material from this work should have provided ample opportunity for micropalaeontologists to study ostracods (Crustacea) from the intervals not available at the surface, however this opportunity has not been taken up. The only subsurface Australian ostracod assemblages described from the Paleogene has been Eglington (2006; Section 2 herein). In 1970/1972 the author acquired samples and residues from four Otway Basin boreholes. At that time these were processed, washed and sieved but no further work carried out. In the interim Neil (1997) examined the Pember Mudstone from Kaladbro-2 and Mumbannar-1 bores but that material did not yield ostracods. Sulphides in the older cores may have resulted in the destruction of calcitic microfossils during storage (Taylor 1965; Eglington 2006). If this is so, the washed residues and separated specimens in the author’s collection may be the only ostracods to survive from these onshore cores.

The aim of the study was to collect and describe Paleogene Otway Basin Ostracoda (Crustacea) from locations not previously sampled for ostracods, and to use these taxa and assemblages for biostratigraphic, palaeoenvironmental and palaeogeographic interpretation.

Approximately 320 subsurface and outcrop samples were treated and examined for ostracods. With ~250 samples from the four boreholes alone, the quantity of material was too great for this study. Accordingly, the decision was made to concentrate on the oldest strata first, i.e. the latest Paleocene–Early Eocene assemblages from Latrobe-1 bore, Rivernook outcrop (Eglington 2006; Sections 2 and 3 herein) and Heywood-10 (Section 2 herein). The Heywood-10 Early Oligocene Narrawaturk-2 Formation was selected as no ostracod assemblages had previously been described from that unit (Section 6 herein). The Late Oligocene Gellibrand Marl was chosen (Section 7 herein) because the only other assemblages described from the Marl were of Miocene age (McKenzie et al. 1991; Neil 1995).

Samples were treated with hydrogen peroxide, sieved and the ostracods picked out under an Olympus stereoscopic microscope. Residues from previous studies were re-washed, re-sieved and picked. Most specimens selected for photography were mounted on carbon tabs and gold coated. Some were too rare and fragile thus were photographed uncoated so as not to obscure subsurface detail. These were photographed under low vacuum with backscatter. At the start of the study photography was carried out on a JEOL JSM 840 scanning electron microscope, later images were from a newer model JEOL JSM 648 OLA scanning electron microscope. Specimens, in particular central muscle scars and marginal pore canals, were photographed with an Olympus Camedia C-5060 camera and attachment on the Olympus stereo-microscope and the images processed in Photoshop using the techniques developed (Section 10).

All Victorian specimens are to be housed in the Palaeontology Section of the Museum of Victoria, Melbourne. The specimens from the McKenzie Collection are to be returned to the Australian Museum, College Street, Sydney and will be transferred from the Marine Invertebrates Section to the Palaeontology Section.

The first section described was a 137 m interval from Latrobe-1 borehole, the remainder of the core was barren of ostracods. The 20 assemblages of latest Paleocene–Early Eocene, and

2 the constituent taxa, were described (Section 2 herein), and used as the basis for further taxonomic study (Sections 3, 4 and 8), and for palaeoenvironmental analysis (Section 5 herein).

The Latrobe-1 assemblages (Section 2 herein), availability of Early Eocene Rivernook Member specimens, and extensive foraminiferal data from the Latrobe-1 bore, provided the opportunity to extend the ostracod descriptions and to make comparisons between the assemblages (Section 3 herein). The data was used to assess the palaeoenvironment (Section 5 herein). The Platycopid Signal Hypothesis for assessing benthic dissolved O2 levels at the substrate (Whatley et al. 2003) was applied and the validity of the technique assessed by comparing the results to the foraminiferal data.

Problems of identification and classification emerged within the genus Cytherella. This concerned certain specimens of very similar size, shape and occurrence that differed according to which valve was the larger. The pool of specimens for comparison was widened to include samples from outcrop and subsurface intervals not otherwise covered in the study. From this wider resource it was possible to identify related taxa and lineages, and to clarify the issues of concern (Section 4 herein).

Heywood-10 bore core included two ostracod-bearing Oligocene sections that were not productive in the Latrobe-1 bore, one Early and the other Late Oligocene. The composition and diversity of the two reasonably large assemblages obtained was discussed, and comparisons made with other assemblages of similar age from South Australia and Victoria.

The analysis and comparisons included the use of the reciprocal of Simpson's Diversity Index (D): D = ∑ n(n-1) N(N-1) [n = total number of organisms of a particular taxon, N = total number of organisms of all species]. The environment for the two Heywood-10 assemblages was assessed according to their composition (Sections 6 and 7 herein).

As the assemblages provided new taxa, taxonomy was an essential and extensive element of the research. Low specimen counts resulted in many new taxa remaining in open nomenclature awaiting additional specimens. Both new and described taxa challenged some pre-existing identifications and extended our knowledge of the stratigraphic and geographic range of the ostracods concerned.

The combination of the particular geographic limitations imposed by the AAG, and the distinctive characteristics of some of the ostracods enabled interpretations concerning the dating of two palaeogeographic events: these were the presence of an early south-flowing current down the West Australian coast (Section 9 herein), and a possible marine connection between the AAG and the Tasman Sea (Sections 8 herein) earlier than the significant breaching near the Eocene/Oligocene boundary (Exon et al. 2004a, 2004b).

During the course of the research, a technique was devised to enhance images of microscopic specimens by using digital photography and digital editing techniques (Section 10 herein). This technique was used to provide images of hard-to-photograph subsurface features such as central muscle scars and marginal pore canals (Sections 4 and 8). The section has been prepared for publication with as a practical set of steps to introduce the method to workers in the fields of biology and micropalaeontology.

References

ABELE, C., KENLEY, P. R., HOLDGATE, G. & RIPPER, D., 1993. Chapter 8 – Tertiary, Otway Basin. In Geology of Victoria, J. G. Douglas & J. A. Ferguson, eds, Special Publication 5, revised edition, Geological Society of Australia, 272-303. BENSON, R. H., 1978. 35 – The Paleoecology of the Ostracodes of DSDP Leg 42A. Deep Sea Drilling Project Initial Reports Volume 42 Part1, 777-787. BERNECKER, T. (Coordinator), Smith, M. A., HILL, K. A. & CONSTANTINE, A. E., 2003. 13 Oil and gas. In Geology of Victoria, W. D. Birch, ed., Geological Society of Australia, Special Publication 23, Victoria, 470-487. DUDDY, I. R., 2003. Chapter 9 – Mesozoic a time of change. In Geology of Victoria, W. D. Birch, ed., Special Publication 23, Geological Society of Australia, Victoria, 239-286. EGLINGTON, C., 2006. Paleogene Ostracoda (Crustacea) from the Wangerrip Group, Latrobe-1 bore, Otway Basin, Victoria, Australia. Proceedings of the Royal Society of Victoria 118(1), 87-111. EXON, N. F., KENNETT, J. P. & MALONE, M. J., 2004a. Preface. In The Cenozoic Southern Ocean, Tectonics, Sedimentation, and Climate Change Between Australia and Antarctica, N. F. Exon, J. P. Kennett & M. J. Malone eds, Geophysics Monograph 151, American Geophysical Union, Washington D.C, vii-viii. EXON, N. F., KENNETT, J. P. & MALONE, M. J., 2004b. Leg 189 synthesis, Cretaceous - Holocene history of the Tasmanian Gateway. In The Proceedings of the Ocean Drilling Program, Scientific Results, 189, N. F. Exon, J. P. Kennett & M. J. Malone eds. http,//www.odp.tamu.edu/publications/189 HOLDGATE, G. R. & GALLAGHER, S. J., 2003. Chapter 10 – Tertiary. In Geology of Victoria, W. D. Birch, ed., Special Publication 23, Geological Society of Australia, Victoria, 289-335. MCKENZIE, K. G., REYMENT, R. A. & REYMENT, E. R., 1991. Eocene-Oligocene Ostracoda from South Australia and Victoria, Australia. Revista Española de Paleontologia 6(2), 135-175. NEIL, J. V., 1997. A Late Palaeocene ostracode fauna from the Pebble Point Formation, south-west Victoria. Proceedings of the Royal Society of Victoria 109, 167-197. TAYLOR, D. J., 1965. Preservation, composition, and significance of Victorian Lower Tertiary ‘Cyclammina faunas’. Proceedings of the Royal Society of Victoria, N.S. 78(2), 143-160. VAN MORKHOVEN, F. P. C. M., 1963. Post-Palaeozoic Ostracoda, Their Morphology, Taxonomy and Economic Use. Volume 2. Elsevier, Amsterdam, London, New York, 1- 478. WOPFNER, H. & DOUGLAS, J. G., 1971a. Chapter 1 – Area and regional setting. In: The Otway Basin of Southeastern Australia. H. Wopfner & J. G. Douglas, eds, Special Bulletin, Geological Surveys of South Australia and Victoria, Ministry of Development and Mines, South Australia and Ministry of Mines, Victoria, 17-25. WOPFNER, H. & DOUGLAS, J. G., 1971b. Chapter 2 – Previous work and exploration history. In The Otway Basin of Southeastern Australia. H. Wopfner & J. G. Douglas, eds, Special Bulletin, Geological Surveys of South Australia and Victoria, Ministry of Development and Mines, South Australia and Ministry of Mines, Victoria, 27- 43.

SECTION 2

PALEOGENE OSTRACODA (CRUSTACEA) FROM THE WANGERRIP GROUP, LATROBE-1 BORE, OTWAY BASIN, VICTORIA, AUSTRALIA

COL EGLINGTON

Department of Earth and Planetary Sciences, Macquarie University, Sydney, New South Wales, 2109, Australia. [email protected]

EGLINGTON, C. Paleogene Ostracoda (Crustacea) from the Wangerrip Group, Latrobe-1 bore, Otway Basin, Victoria, Australia. Proceedings of the Royal Society of Victoria.

Key words. Paleogene, Ostracoda, Wangerrip Group, Latrobe-1 bore, Otway Basin, Victoria, Australia, taxonomy, Paleocene-Eocene boundary, Rivernook, Princetown.

ABSTRACT

Twenty-two Paleogene (latest Paleocene–earliest Eocene) marine ostracod assemblages from subsurface Wangerrip Group units in the Latrobe-1 bore, Otway Basin, southern Victoria, Australia, are described and discussed. Twenty three taxa from nine families are represented, two species are new, Neobuntonia taylori sp. nov. and Tasmanocypris? latrobensis sp. nov., seven species are confirmed, six are inconclusive and eight are under open nomenclature due to insufficient material. The study extends the time and geographic range of most of the genera and species obtained.

INTRODUCTION

Several descriptions and analyses of ostracod faunas from Paleogene surface sections of southeastern Australia have been published recently, however this taxonomic study is the first to describe subsurface Otway Basin Paleogene Ostracoda. The borehole section studied ranged from Late Paleocene, across the Paleocene/Eocene boundary and into Early Eocene with ostracod assemblages from three significant marine ingressions occurring through this interval: the Rivernook A, Rivernook and Princetown ingressions.

PREVIOUS OSTRACOD STUDIES

The Paleogene Ostracoda of southeastern Australia received no attention until 1943 when Crespin’s exhaustive study of Gippsland Basin bores listed the occurrences of 72 ostracod species of which 37 were from Oligocene strata although at the time she had dated them as Middle Miocene (Crespin 1943). Unfortunately many of her identifications were based on Recent species, in particular Brady (1866, 1880) that often relied on European taxa of similar appearance. Crespin also identified species as conspecific with Miocene and younger faunas (Chapman 1914; Chapman et al. 1928) whose authors had also relied on Brady’s work. This resulted in a large number of misidentifications (McKenzie 1981) and these, combined with her lack of illustrations or descriptions, greatly reduced its usefulness.

From 1943 to 1973 the region’s Paleogene ostracods were occasionally mentioned in wider ranging studies, as faunal lists or in synonymies such as those of Hornibrook (1952), Nadeau (1955), Van Morkhoven (1962), McKenzie (1967, 1973) and Benson (1972). McKenzie (1974), in discussing Cenozoic ostracods of southeastern Australia, included several

Paleogene strata with ostracod assemblages and their palaeoenvironments. This was followed by his analysis of species distribution in the Australian Cenozoic in terms of biogeographic patterns (McKenzie 1978), and briefly in the Tethyan context (McKenzie 1983). His studies of borehole faunas from the Willunga Embayment, St. Vincent Basin (McKenzie 1979), though short, provided much-needed data for taxonomic and biostratigraphic work. McKenzie (1981) followed up with an important and clarifying taxonomic revision of the Chapman/Crespin Mallee and Sorrento bores. The earlier Willunga Embayment study was succeeded by a related discussion on the use of ostracods as petroleum-potential indicators across the Eocene/Oligocene boundary (McKenzie & Guha 1987).

During the 1990s a number of studies greatly enhanced the knowledge of southeastern Australian Paleogene ostracod assemblages, they were: the Eocene/Oligocene faunas from the Gull Rock Member of the Blanche Point Formation, St. Vincent Basin and Jan Juc Formation in the Otway Basin (McKenzie et al. 1991); the Eocene Browns Creek Clays of the Aire District, Otway Basin (McKenzie et al. 1993); Oligocene/Miocene palaeobiogeography within basins in Victoria, South Australia and Tasmania (Neil 1995); the Late Eocene Blanche Point Formation, St. Vincent Basin of South Australia (Majoran 1995; Majoran 1996a); the Eocene/Oligocene boundary in the Chinaman’s Gully Formation (Majoran 1996b); cytheropterine ostracods of the Port Willunga Formation (Majoran 1997) and, finally, the Late Paleocene fauna from the Pebble Point Formation, Otway Basin providing the oldest Cenozoic ostracods for this region (Neil 1997).

There are no published studies of ostracods from the Dilwyn Formation, or from any subsurface sections of the Otway Basin Paleogene. Neil (1997) examined the Pember Mudstone from Kaladbro-2 and Mumbannar-1 bores but that material did not yield ostracods. Relevant micropalaeontological studies have been primarily foraminiferal and palynological, in particular Taylor (1964, 1965, 1967, 1971), McGowran (1965, 1970, 1989, 1991) McGowran et al. (1971, 1997), Harris (1971, 1993), Stover & Partridge (1973) and Tickell et al. (1993).

LOCATION OF AND BACKGROUND TO THE PRESENT STUDY

The Latrobe-1 borehole is located on the coast of SW Victoria (Fig. 1), west of the town of Princetown and approximately 1.65 km northwest of Point Ronald. Location details from the Geological Survey of Victoria borehole system (GEDIS) log are: Princetown (7520.4.2) 1:25,000 Topographic Map, easting 686501, northing 5714955, latitude 38.69424º, longitude 143.14447º. Structurally it is within the southeastern Otway Basin between the Tyrendarra and Port Campbell Embayments.

Completed in 1963, the bore was sited close to the Wangerrip Group type section to intersect the unexposed interval between the Princetown Member and the Clifton Formation. It bottomed at 626 m, well into the underlying Cretaceous sedimentary rocks and, though coring was virtually continuous, there are within the section numerous gaps (Table 1). Because of the quantity of core overall, and its strategic position, the bore has been of particular interest for defining and correlating the regional stratigraphy, and is referred to in many reports and studies, particularly in Wopfner & Douglas (1971) and Douglas & Ferguson (1976, 1988, 1993).

In spite of its apparent potential, the bore’s microfauna proved disappointing, with Ostracoda only found between 211 m and 344.4 m. Foraminiferal numbers were also either greatly reduced or entirely absent in samples outside of this interval (Taylor pers. comm. 1970). Some of this deficiency is due to paralic/transgressive/regressive depositional conditions of

6 non-deposition, disturbance or erosion of sediments, and periods of adverse environmental conditions such as stagnant or restricted circulation or disturbed salinity levels. Ostracods are absent in otherwise promising marine beds that contain foraminifera, the probable reason for this being their dissolution by sulphuric acid generated from the breakdown of pyrites to copiapite and jarrosite within the strata (Taylor 1965). That the foraminifera survived is possibly due to their thicker and more resilient tests. The unfavourable chemical conditions are not all pervasive, excellently preserved specimens were present in limonitic samples indicative of oxidising conditions. High specimen numbers did not necessarily equate with good conditions for preservation in situ, some of the relatively rich assemblages had fragile, corroded specimens (eg. 47A, 47B) whereas other samples with low counts contained superbly preserved material (eg. 45B, 54C, 58A)

Fig. 1. Site of the Latrobe-1 borehole near Princetown and neighbouring locations of Rivernook and Pebble Point, Otway Basin, Victoria.

Samples for this study were those on which Taylor (1964, 1965, 1971) based his foraminiferal work. This research also provides information on ostracod-bearing strata in the region of this age, data on subsurface ostracod assemblages, contributes to information on the range of species previously described from Eocene and younger horizons, and provides additional faunal data across the Paleocene/Eocene boundary.

STRATIGRAPHY

Below 30-60 m the Latrobe-1 bore intersects the Cenozoic Heytesbury, Nirranda and Wangerrip Groups then the Mesozoic Sherbrook and Otway Groups, only the Wangerrip Group produced ostracods.

The relevant formation within the Wangerrip Group is the Dilwyn (Late Paleocene-Early Eocene). It is interpreted as a paralic sequence of transgressive-regressive cycles resulting in fluctuating marine to brackish estuarine conditions (Bock & Glenie 1965; Glenie 1971; Holdgate & Gallagher 2003). Taylor (1971) analysed several foraminiferal assemblages including Latrobe-1 and concluded that the depositional environment was marginal marine with sudden, sporadic marine breakthroughs producing periodic rich marine faunas. The Dilwyn Formation is widespread subsurface and consists predominantly of quartz sandstone, often silty or clayey, sandy siltstone and claystone, mudstone and shale. The finer grade sedimentary rocks are commonly dark, carbonaceous, micaceous and pyritic. In this bore the formation was identified from a depth of 70.10– ~345 m (GEDIS). Of the Dilwyn subunits,

7 often restricted in occurrence, six are relevant to this study, they are the Princetown, Rivernook and Pember Mudstone Members, and the minor units, the Trochocyathus, Turritella and Rivernook A beds. The Princetown, Rivernook and Rivernook A units are interpreted as ingressions, with each sub-unit containing its own distinctive faunal assemblage (McGowran 1965, 1970, 1991; Taylor 1964, 1965, 1971). The use of the names of the minor units has been retained to facilitate referral to these short stratigraphic intervals and to correlate them with Taylor’s foraminiferal faunas.

Taylor (Taylor 1964, 1965) identified distinctive foraminiferal assemblages from both outcrop and subsurface. In his earlier report (Taylor 1964) he named these the Princetown, Trochocyathus, Rivernook and Pebble Point faunas, relating them to the stratigraphic units in which each “faunas” predominantly occurred. For dating purposes he later replaced these faunas with a system of lettered zonules (Taylor 1971). The reference section for these zonules is Latrobe-1, there are only very minor change in the depth positions for the zonules compared to the previous faunal positions (Taylor 1964). Though the zonules have had some degree of recognition and usage, they are chronostratigraphic units, the faunals were more appropriate for this study.

Though fauna is sparse in the outcropping Princetown Member at Princetown, Taylor (1965) was able to correlate its characteristic foraminiferal assemblage in Latrobe-1 identify the Princetown Member at 228.6 m and designate 207.26–256.03 m as Princetown Fauna. The Trochocyathus and Turritella beds are thin, fossiliferous units, first observed nearby in outcrop (Baker 1943, 1944, 1950). Taylor (1964) identified 256.03–289.56 m as Trochocyathus Fauna but did not indicate the bed position within the bore section. Positions for these beds in the bore have not previously been indicated, the suggested positions have been derived from the faunal concentrations, and by the relative positions of the beds compared to the surface section based on Taylor's (pers. comm. 1970) unpublished foraminiferal assemblage charts. It is suggested that the Turritella Bed lies between ~262 and 264.5 m, the Trochocyathus Bed is intersected at 257.84 m, and the Princetown Member between ~207 and ~229 m.

The basal unit of the Dilwyn Formation in Latrobe-1 is the Pember Mudstone. The Pember Mudstone is nearly 60 m thick and conformably overlies the Paleocene Pebble Point Formation. Although the top is generally placed at 288/289 m and the bottom at 343.5/347 m (GEDIS), the most likely position of the base would appear to be just below the lowest occurrence of ostracods at 344.42 m. Just above the base of the Pember Mudstone are two minor units, the Rivernook Member and Rivernook A Bed.

The Rivernook Member outcrops in a coastal exposure of the Dilwyn Formation between Point Ronald and Moonlight Head. There it consists of 6 m of glauconitic and limonitic sandstone and claystone with a lower bed that is usually concealed by beach sand referred to as Rivernook A Bed, also of glauconitic and micaceous silty claystone (McGowran 1970; Abele, Kenley et al. 1993). In Latrobe-1 Taylor (1964, 1965) identified the Rivernook Fauna at 289.56–305.4 m but did not indicate the stratigraphic interval for the Rivernook units. In his unpublished data (Taylor pers. comm. 1970) marked a position for Rivernook A at 304.8 m. McGowran used his own and Taylor’s earlier work to describe the identifying features of the foraminiferal fauna from Rivernook A (McGowran 1970). Based on the available information including Taylor pers. comm. (1970), and the ostracod concentrations, it is suggested that the Rivernook A Bed in Latrobe-1 lies at approximately 304.5–305.5 m. It probably grades directly into the overlying Rivernook Member which extends to ~292 m. Taylor’s faunas usually extend beyond the stratigraphic units of the same names, for instance

Taylor in identifying the Pebble Point Fauna from 305.41–335.28 m commented that it ranged well above the Pebble Point Formation (Taylor 1964).

The importance of the Rivernook, Rivernook A and Princetown assemblages has been greatly enhanced with their being linked to the broader Australian palaeohistory and to three ingressions of the same names that are regarded as significant marker events at, or near, the Paleocene/Eocene boundary (McGowran 1965, 1970, 1989, 1991; McGowran et al. 1997; Chaproniere, Shafik, Truswell, Macphail & Partridge 1996).

AGE

The top of the study section at 207.26 m is within the Stover & Partridge (1973) spore-pollen Malvacippolis diversus Zone, the base at 344.42 m is within the Upper Lygistepollenites balmei Zone, dated as Early Eocene and Late Paleocene respectively (Partridge & Dettmann 2003). Positions for spore/pollen zones and sub-zones (table 1) were obtained from the Latrobe-1 bore logs and associated reports (GEDIS; Harris 1971, 1993; Archer 1977; Tickell et al. 1993; Stough in Partridge pers. comm. 2006; Partridge pers. comm. 2006).

The section spans the Paleocene-Eocene boundary, the exact placement of which is problematic. After this manuscript had been completed additional unpublished information from several sources became available that may upon further investigation clarify the boundary but it is beyond the scope of this predominantly taxonomic study. The interval in question includes the Spinizonocolpites prominatus Subzone, the Upper L. balmei/Lower M. diversus boundary and the Rivernook A ingression and will be treated as a boundary interval of ?latest Paleocene/?earliest Eocene age.

MATERIAL STUDIED

In 1970 Taylor loaned the author 107 of his 250 Latrobe-1 residues used for his foraminiferal studies (Taylor 1964, 1965, 1971). Taylor collected and treated 200 gm samples, for this study these residues were separated by sieving into course (>1.4 mm), medium (0.3–1.4 mm) and fine (<0.3 mm) fractions, and picked with 21 of the 107 samples yielding ostracods. The productive samples were from the interval 211.23 m to 344.42 m (samples 40A–64), though within this interval Taylor’s sampling log (pers. comm. 1970) recorded numerous missing intervals of core not evident in the GEDIS log. Not all unproductive samples have been included in table 1. Residue sizes varied from a few grams to up to 100 gm depending on the clay content removed in initial washing. When present, the ostracod frequency was usually very low. Many specimens were severely affected by acidic conditions in situ leaving surviving shells fragile, though by contrast, some were in excellent condition. In the years subsequent to initial collection some specimens were lost or broken through transportation, storage accidents and slide damage.

COMMENTS ON THE FAUNA

Due to such small numbers, a statistical analysis would be misleading. Faunal representation will be discussed both quantitatively and qualitatively but, based on this material, the former should be viewed as a guide to taxa represented.

There was a total of 242 specimens across nine families, 15 genera and 23 species. Two species are new, Neobuntonia taylori sp. nov. and Tasmanocypris? latrobensis sp. nov.; seven species identifications are confirmed; six are inconclusive for reasons discussed and eight are

9 under open nomenclature due to insufficient material. Most of the forms extend the range of genera or species. The families represented were:

 CYTHERELLIDAE: Two genera: Cytherella, 3 species; Cytherelloidea, 3 species.  PARACYPRIDIDAE: Two genera: Paracypris, 1 species; Tasmanocypris?, 2 species.  BAIRDIIDAE: One genus: Neonesidea, 1 species.  LOXOCONCHIDAE: Two genera: Loxoconcha and Kuiperiana, 1 species each.  XESTOLEBERIDIDAE?: Allocation tentative, 1 specimen.  BYTHOCYTHERIDAE: One genus: Cytheralison, 2 species.  PECTOCYTHERIDAE: One genus: Munseyella, 1 species.  HEMICYTHERIDAE: One genus: Neobuntonia, 1 species.  TRACHYLEBERIDIDAE: Three genera: Trachyleberis, 2 species; Echinocythereis, 1 species; Cletocythereis, 1 species.  Incertae sedis: 1 species.

Three species were markedly smaller in size than those from other areas, they were Neonesidea aff. N. australis, Trachyleberis thomsoni? and Cytherelloidea jugifera. These taxa may represent dwarf forms indicative of a population under environmental stress (Section 3 herein).

THE OSTRACOD ASSEMBLAGES.

The ostracod assemblages occur within Taylor’s foraminiferal faunas (Taylor 1964) corresponding to periods of ingression with more favourable marine conditions. Within these ingressions are intervals with no fauna of any type, or with very low representation. Although some of these incidents may be due to poor preservation, in others there are indications that adverse environmental conditions were responsible (Section 5 herein). The high sampling frequency within these intervals provides a level of detail not often available, so a more detailed study, with additional data, has been presented in Section 5 here in.

When the ostracod distribution is examined across Taylor’s faunas (table 1) distinctive horizons with respect to specimen numbers and diversity are evident in the Rivernook Fauna, the Turritella Bed, the Turritella Fauna, and in the lowermost and uppermost sections of the Princetown Fauna. These ostracod horizons align with the higher foraminiferal concentrations (Taylor pers. comm. 1970).

Pebble Point fauna. This was the least productive of the faunas, three samples provided five ostracod taxa of which three were long-ranging species, one a shorter-ranging paracyprid, and the fifth a very short-ranging new species Neobuntonia taylori.

Rivernook fauna. Abundance and diversity increase up section within the Rivernook strata, in all there are 15 taxa (90 specimens), 11 species appearing for the first time, six are not found within the section outside this fauna. The prominent horizon at ~296-297 m contained 14 of the 15 taxa.

Trochocyathus fauna. The lower part of this fauna has large sections of missing core, the remainder is quite devoid of ostracods and some samples have no fauna of any type. In the upper section ostracods were found only in the Turritella and Trochocyathus beds, and the interval between them. The Turritella Bed is the most evident ostracod horizon in this fauna yielding 12 taxa (82 specimens), from two samples. Five species appear for the first time, only one of these, Echinocythereis karooma, extends beyond the fauna, the other four cannot

Paleocene/Eocene Earliest Late Paleocene Early Eocene Boundary Eocene Chronostratigraphy Thanetian Interval PETM Ypresian L. b./M. d. Upper Lygistepollenites 314 Lower M. Spore/pollen Zones Indeterminate Malvacipollis diversus (undifferentiated) balmei diversus (adapted from GEDIS; transition

296.9 Harris 1971, 1993; Archer 1977; S. prominatus 281.9 Tickell et al. 1993; Partridge pers.

Subzone comms 2006)

P6a?

P6b P5 P7 Foram. Zones (McGowran 1991;

Holdgate & Gallagher 2003)

335.28

289.56

256.03 207.25 305.4 Foraminiferal Faunas Pebble Point Rivernook Trochocyathus Fauna Princetown Fauna (Taylor 1964)

Fauna Fauna ~70

WANGERRIP GROUP / DILWYN FORMATION

Turr

Troc

River-

nook ~229.5

Riv.A Proposed Positions of

Mem.

264.5

~292

~257

D.F. . Bed .

Pember Mudstone Member Bed . Princetown Member Stratigraphic Units

………

……….

.. ..

. . .

..-..-..-.

......

.. ..

......

. Stratigraphic Column

. .

344.42

329.64

319.43

313.64

308.46 308.46

~305

~298-9

~296-7

292.3

289.56

288.65

285.6

281.33

262-265

259-261

257.84

254.2

245.06

229.21

221.89 221.89

211.23 207.25 Sample Positions

Depth in metres

[recovered

[corenot

61 A 61

58 A 58

56 bottom 56

56B

56 agg. 56

54F-55 agg. 54F-55

54-C agg. 54-C

53B

47 A/B, 47 860'

46 A/B 46

45B

44B

43B

40A Total

Sample Number

7 1

1 Glencoeleberis ? thomsoni

1 3

2 Neobuntonia taylori

2 ?

1 Paracypris sp.

2 6

3 Cytherella sp. cf. C. atypica

1 1

1 Cytherella sp.

3 2

1 Tasmanocypris ? sp.

1 5

1 T. ? latrobensis

4 9

4 Cytherelloidea jugifera

2 3

4 Glencoeleberis? thomsoni var. A 1

1 Kuiperiana .cf. K. lindsayi 1

1 Xestoleberis ? sp. 1

1 Cytherelloidea hrycga ? 1

1 Cletocythereis kurrawa 2

2 Munseyella dunoona

1 2

1 Cytherella pinnata

6 3

1 Neonesidea aff. Australis 1

1 Indet. Gen. sp. 1

1 Cytheralison corrugata ? 1

1 Cytheralison sp.

3 1

1 Echinocythereis karooma 1

1 Loxoconcha sp.

2 1

1 ?Trachyleberis ? sp. 3

3 Cytherelloidea praeauricula

245

9 2

9 Total

glauconite

shellfrags

shellfrags NFF

NFF Foraminifera Present (X)

X X X or other indications of marine environment

Distribution of early Palaeogene Ostracoda, chronostratigraphy and faunal units in Latrobe-1 borehole, aggregated samples are Table 1 broken down in Table 2, (NFF = no fauna of any type found).

Table 1. Distribution of early Paleogene Ostracoda, chronostratigraphy and faunas in Latrobe-1 borehole, aggregated samples are broken down in Table 2, NFF = no fauna of any type found.

var. var.

(large)

sp. nov. sp.

N.australis

K. lindsayi

C. atypica.

sp. nov. sp.

? sp. ?

sp.

Faunas

? sp. ?

sp. aff. aff. sp.

sp. cf. sp.

sp.

sp. cf. sp. sp.

Depth (in metres) Depth (in

Sample Number Sample Glencoeleberis? thomsoni Glencoeleberis? Neobuntonia taylori taylori Neobuntonia

Cytherella Cytherella Cytherella Cytherella Tasmanocypris T.? Latrobensis T.? Latrobensis Cytherelloidea jugifera Cytherelloidea

Kuiperiana Kuiperiana Xestoleberis

Cletocythereis kurrawa Cletocythereis Munseyella dunoona Munseyella Cytherella pinnata Cytherella Neonesidea Neonesidea

Taylor's (1964) Foraminiferal (1964) Taylor's

Stratigraphic Units Stratigraphic

Paracypris Paracypris

Glencoeleberis? thomsoni thomsoni Glencoeleberis?

Cytherelloidea hrycga Cytherelloidea

Indet. gen. and sp. and gen. Indet. Cytheralison corrugata Cytheralison Cytheralison Cytheralison Echinocythereis karooma Echinocythereis Loxoconcha Loxoconcha Total

Foraminifera (or other other (or Foraminifera marine indicators) marine

Dil. Dil. Fm. 254.20 45A 0 Troc. 257.80 45B 3 2 3 1 9 259.40 46A 1 1

Fm.

Dil. Dil.

Fauna 260.60 46B 4 1 3 1 2 3 14 262.10 860-2' 5 1 6 262.70 47A Bed 6 15 4 1 1 5 4 1 37

Turritella 264.60 47B 4 5 8 1 5 2 1 1 1 11 39 288.40 48A

Trochocyathus

289.56 52C 0

Dilwyn Fm. Dilwyn 292.30 53B 2 7 1 10 X

295.35 54 1 1 10 1 13 X ~295.96 54 A 1 1 13 1 3 1 1 1 2 8 32 X ~296.50 54 B 1 15 1 1 1 1 20 X ~297.00 54 C 1 1 1 3 ~297.50 54D NFF ~298.00 54E NFF

Rivernook Fauna Rivernook

Rivernook Member Member Rivernook ~298.50 54 F 3 1 1 5 X 299.62 55 1 ? 2 ~302.00 55A trace ~303.60 55B glauconite NFF

Riv. A 304.80 56 top 2 2 X 305.41 56A 2 ? 3 X

Total 21 5 1 76 3 3 11 15 7 1 1 1 1 2 22 7 1 1 1 15 1 196

Table 2. Breakdown of distribution of ostracod species in Latrobe-1 borehole from samples aggregated in Table 1, NFF = no fauna found. be identified with certainty. Despite the high specimen yield, the preservation of the specimens was generally poor. The more impoverished Trochocyathus Bed had four species, in all nine specimens, but with a much better level of preservation, some specimens in pristine condition.

Princetown fauna. Within this 50 m unit there are only three ostracod-bearing samples of which the 229.21 m horizon, at or near the base of the Princetown Member, is the most productive, it contained 33 well preserved specimens across eight taxa,. The horizon at the top of the section has only 9 specimens from 7 taxa, none are new to this horizon, all except the unidentified Trachyleberis? sp. are long-ranging within the section, four are found in younger strata elsewhere, they are Trachyleberis thomsoni, Cytherella sp. cf. C. atypica, Cytherella

12 pinnata and Echinocythereis karooma (McKenzie et al. 1991, 1993; Sections 3 & 4 herein). This horizon’s prominence is enhanced by the absence of any ostracods above it.

TAXONOMY

The following conventions and abbreviations are used; C articulated carapace; LV left valve; RV right valve; F female; M male; juv. juvenile; A adult; A1 final stage instar; CMS central muscle scars; ~ approximate (depth); numbers with P prefix are registered with the Museum Victoria. SEMs have all been reproportioned to correct for inherent software errors.

Order PODOCOPIDA Müller 1894 Suborder PLATYCOPA Sars 1866 Family CYTHERELLIDAE Sars 1866 Cytherella Jones 1849 Cytherella sp. cf. C. atypica Bate 1972 Figs 2G-N, P

Affinities Cytherella atypica Bate 1972: 4, Pl. 3, figs 1-4, Text Figs 2A, 2B, 2D, 3F. Cytherella sp. Whatley & Downing 1983: 385, Pl. 8, figs 6-8. Cytherella cf. C. pinnata – Neil 1997: Fig. 4C.

Remarks. Smooth, ovate cytherellid with left valve overlapping right and twin brood chambers in the female. This material fits the description of Cytherella atypica Bate (1972), the only hesitancy to unequivocal identification is due to a consistent feature at variance with C. atypica (in Bate 1972, Text Fig. 2D) in the anterior selvage of C. sp. cf. C. atypica. In Cytherella sp. cf. C. atypica the outer rim of the anterior interior margin of the larger (left) valve is reduced and stepped down on the outermost edge rather than having the bulging lip present in the remainder of the marginal outer edge of the larger valve. The size range is consistent with Cytherella atypica. Whatley & Downing (1983) regarded their Cytherella sp. as not C. atypica due to their specimens being larger in size and having a “slightly umbonate dorsal margin”. When comparing sizes and shape it was felt these were insufficiently divergent to be accorded separate species status. Size comparisons in millimetres are as follows: Cytherella atypica Bate, 1972 AFs: length, 0.79–0.85 mm, height, 0.5–0.59 mm. AMs: length, 0.81–0.83 mm, height, 0.51–0.56 mm. Cytherella sp. Whatley & Downing, 1983 AFs: length, 0.9–0.92 mm, height, 0.59–0.6 mm. AMs: length, 0.81 mm, height, 0.49 mm. Cytherella sp. cf. C. atypica AFs: length, 0.75–0.975 mm, height, 0.53–0.6 mm. AMs: length, 0.7–0.875 mm, height, 0.525–0.61 mm.

Whereas Cytherella sp. Whatley & Downing (1983) has adult females larger than females of C. atypica Bate (1972), the males of both are the same size. When the three forms are compared Cytherella sp. cf. C. atypica spans the size ranges of the other two. It is also possible that those identified as small adults are precocious final stage juveniles. As to the umbonate dorsal outline of Cytherella atypica Bate (1972), when outlines of specimens of C. sp. cf. C. atypica are examined some are more convex than others. These shape variations

13 between the three populations may well be no more than a reflection of environmental or phylogenetic factors and some degree of intraspecific variation.

Neil's (1997) figured specimen 4C of Cytherella cf. C. pinnata right valve has the stepped- down margin of the smaller valve; it could therefore be C. atypica or a close affinity.

Cytherella sp. cf. C. atypica is the second longest-ranging species in the section and by far the most numerous (the taxonomy of this species is discussed in much greater detail in Section 4 herein).

Measurements. RVF: length 0.8 mm, height 0.5 mm. RVF: length 0.91 mm, height 0.6 mm. RVM: length 0.98 mm, height 0.58 mm. LV: length 0.83 mm, height 0.55 mm. LVM: length 0.6 mm, height 0.26 mm. LVM: length 0.75 mm, height 0.54 mm. CF: length 0.8 mm, height 0.5 mm, breadth 0.38 mm. CF: length 0.75 mm, height 0.52 mm, breadth 0.4 mm.

Material. 82 adult and juvenile specimens plus fragments.

Figured specimens. Figs 2G, I, N (P312757), sample 46B at 260.60 m; Figs 2H, M, P (P312758), sample 54 at 295.35 m; Fig. 2J (P312755), sample 54 at 295.35 m; Fig. 2K (P312756), sample 58A at 313.64 m; Fig. 2L (P 312759) sample 43B at 229.21 m.

Location and age. Latrobe-1 bore, Dilwyn Formation including Pember Mudstone from 313.64–211.23 m; Late Paleocene–Early Eocene.

Cytherella pinnata McKenzie, Reyment & Reyment 1993 Figs 2A-F

Cytherella pinnata McKenzie, Reyment & Reyment 1993: 78, Pl. 1, figs 1, 2. Cytherella cf. C. pinnata – Neil 1997: 170, Fig. 9F.

Remarks. This Cytherella was noted by its authors to have the normal cytherellid right-over-left valve overlap, plus two brood chambers in the adult females. Cytherella pinnata bears a close resemblance to C. atypica Bate (1972) and to C. sp. cf. C. atypica of this paper in overall size, shape, appearance and in having twin brood pouches. However Cytherella atypica has reversed overlap of left-over-right. Both species occur in this section, often in the same samples. As they are almost identical the only simple criterion for identifying them was the overlap. The distinctive adductor muscle scars in Cytherella pinnata mentioned by its authors were not observed (the taxonomy of this species is discussed in much greater detail in Section 4 herein).

The right valve of Cytherella sp. cf. C. pinnata of Neil (1997: 4C) has the reversed overlap seen in C. atypica and is therefore not C. pinnata which displays the normal R>LV overlap.

Measurements. Average FLV length 0.9–0.92 mm, height 0.5–0.55 mm.

Material. 23 specimens of adults and juveniles of both sexes.

Figured specimens. Fig. 2A (P312750), sample 54A at ~ 295.96 m; Figs 2B, C (P312751), sample 47A at 262.74 m; Figs 2D, F (P312752), sample 54A at ~295.96 m; Fig. 2E (P312753), sample 47B at 264.57 m.

Location and age. Latrobe-1 bore, Dilwyn Formation including Rivernook Member, ~295.96–211.23 m; ?latest Paleocene/?earliest Eocene–Early Eocene.

Cytherella sp. Fig. 2O

Remarks. A moderate sized cytherellid, sub-rectangular in lateral view. Anterior margin semicircular; posterior margin broadly rounded in the two available adult females, longest medially. Ventral and dorsal margins slightly concave to slightly convex. Maximum height approximately midway between anterior margin and adductor muscle scars. Maximum breadth just behind the adductor muscle scars depression. RV overlaps LV. Surface overall smooth with fine reticulations observed along the anterior marginal area in the LV. Internally there are two posterior brood chambers. Adductor muscle scars midway along the length, in slight depression and angled diagonally, details could not be discerned.

These specimens do not display the anterior and posterior micropunctae of Early Miocene Cytherella paranitida Whatley & Downing (1983), or the postero-marginal ridge of Late Oligocene C. bellsi McKenzie, Reyment & Reyment (1991) and C. sp. aff. C. bellsi McKenzie, Reyment & Reyment (1993).

Measurements. FLV: length 0.75 mm, height approx. 0.4 mm. FRV: length 0.7 mm, height approx. 0.45 mm.

Material. Two valves, both adult females, two others lost in storage.

Figured specimen. Fig. 2O (P312754), sample 54A at ~295.96 m.

Location and age. Latrobe-1 bore, Dilwyn Formation including Rivernook Member, ?305.41– ~295.96 m; ?latest Paleocene/?earliest Eocene–Early Eocene.

Cytherelloidea Alexander 1929 Cytherelloidea jugifera McKenzie, Reyment & Reyment 1991 Figs 3A-B

Cytherelloidea sp. McKenzie 1979: Pl. 1, fig. 7. Cytherelloidea jugifera McKenzie 1991, Reyment and Reyment: 139, Pl. 1, figs 10-12. Cytherelloidea jugifera – Majoran 1995: Fig. 3F, Appendix Table. Cytherelloidea jugifera – Majoran 1996: 20, 21, 22, 24, Pl. 1, fig. 2, Text Fig. 6, Table 1, Appendices 1, 2.

Remarks. Adults from this location were smaller than the Late Eocene specimens but otherwise conformed.

Measurements. RVF: length 0.875 mm, height 0.54 mm. CF: length 0.83 mm, height 0.5 mm, breadth, 0.375 mm. LV: juv, length 0.7 mm, height 0.45 mm.

Fig. 2.

A-F. Cytherella pinnata McKenzie, Reyment & Reyment 1993.

A. ACLV, P312750. B. AFRV internal, P312751. C. Detail of margin, RV internal, P312751. D. Detail of margin, LV internal, P312752. E. Juv. RV external, P312753. F. AFLV internal, P312752.

G-N. Cytherella sp. cf. C. atypica Bate 1972.

G. AFRV internal, P312757. H. AMLV internal, P312758. I. Adductor muscle scars, RV internal, P312757. J. Juv. RV external, P312755. K. ARV external, P312756. L. AFCRV, P312759. M. Details of margin, LV internal, P312758. N. Details of margin, RV internal, P312757.

O. Cytherella sp., AFLV, P312754.

P. Cytherella sp. cf. C. atypica Bate 1972, details of margin LV internal, P312758.

Q. Cytherelloidea praeauricula (Chapman 1926), AFRV, P312763.

R. Xestoleberis? sp. CLV external, P312760.

Scale bar = 100 microns: A, B C, E, F, G, H, J, K, L, O, Q, R. Scale bar = 10 microns: C, D, I, M, N, P.

Material. Eighteen specimens including one carapace, mostly juveniles.

Figured specimens. Fig. 3A (P312761); fig. 3B (P312762); both from sample 54A at ~295.96 m.

Location and age. Latrobe-1 bore, Dilwyn Formation including Rivernook Member, ?299.62–229.21 m; ?latest Paleocene/?earliest Eocene–Early Eocene.

Cytherelloidea hrycga? McKenzie, Reyment & Reyment 1993 Figs 3C-D

Affinity Cytherelloidea hrycga McKenzie, Reyment & Reyment 1993: 79, Pl. 1, figs 7-9.

Remarks. This one juvenile was dissimilar to juveniles of Cytherelloidea jugifera McKenzie Reyment & Reyment (1991), the ventral ridge of C. hrycga? was narrower, less pronounced and much closer to the posterior margin.

Measurements. LV juv., length 0.8 mm, height 0.46 mm.

Material. One juvenile LV.

Figured specimen. Figs 3C-D (P312790), sample 54A at ~295.96 m.

Location and age. Latrobe-1 bore, Dilwyn Formation, Rivernook Member, ~295.96 m; ?latest Paleocene/?earliest Eocene.

Cytherelloidea praeauricula (Chapman 1926) Fig. 2Q

Cytherella praeauricula Chapman 1926: 105-106, Pl. 22, fig. 9. Cytherella praeauricula – Hornibrook 1952: 24. Cytherelloidea praeauricula – Swanson 1969: 38, Pl. 1, figs 14-16. Cytherelloidea praeauricula – Ayress 1995: 900, 913, Figs 12.8-9, Table 1.

Remarks. This location is the first Australian record of this species, it predates the New Zealand occurrences of Late Eocene (Ayress 1995) to Early Miocene age (Swanson 1969). The small size and distinctive ridging compare well to the illustrations of both Ayress (1995) and Swanson (1969), and to specimens from the Victorian locations of Browns Creek, Castle Cove, Duck Creek and Narrawaturk-2 (Eglington in prep.). The short antero-median ridge connecting the outer and inner concentric ridges is less conspicuous in these earlier Latrobe-1 specimens than in those from the other locations listed, and may reflect an earlier stage in the evolutionary development of this feature.

Measurements. RVF: length 0.63 mm, height 0.40 mm. LV: length 0.60 mm, height 0.37 mm. LV: length 0.55 mm, height 0.28 mm.

Material. Three specimens: one right valve female displaying twin brood pouches, one left valve and one smaller left valve (presumed to be A1 instar).

Figured specimen. Fig. 2Q (P 12763), sample 43B at 229.21 m.

Location and age. Latrobe-1 bore, Dilwyn Formation, Princetown Member, 229.21 m; Early Eocene.

Suborder PODOCOPA Sars 1866 Family PARACYPRIDIDAE Sars 1923 Paracypris Sars 1866 Paracypris sp. Figs 3E-F

Remarks. This identification is based on the sub-triangular shaped valve with maximum height anteriorly. Muscle scars appear to conform to the paracypridid type (Maddocks 1988) but were very indistinct. The hinge is adont The inner margin and line of concrescence do not coincide.

Measurements. Length ~0.8 mm, height 0.41 mm.

Material. One broken left valve. Another possible specimen of this species was found at 329.64 m in the Pember Mudstone but was lost in storage, its identification is based on an earlier sketch.

Figured specimen. Figs 3E-F (P312767), sample 46B at 260.6 m.

Location and age. Latrobe-1, Dilwyn Formation, 260.6 m; Late Paleocene? – Early Eocene.

Tasmanocypris McKenzie 1979 Tasmanocypris? latrobensis sp. nov. Figs 3G-I

Derivation. Named after the location from which it has been described.

Types. Holotype is the specimen P312766, Fig. 3I, Dilwyn Formation at 260.60 m depth (sample 46B). Paratypes are: P312764, Fig. 3G, Dilwyn Formation at 264.57 m (sample 47B) and P312765, Fig. 3H, from 229.21 m (sample 43B).

Diagnosis. Tasmanocypris? with acutely-angled posterior termination in left valve, subacuminate in RV, dorsum arch angled.

Description. Smooth shelled paracypridid, sub-triangular in lateral view with a broadly rounded anterior margin and angular to sub-acuminate posterior termination. Outline of the left larger valve is straight to convex on all margins except for the sometimes slightly concave venter. RV concave antero-dorsally, rising to the angular, arched dorsum, then descending in a straight line from the postero-dorsal angle to the acutely-angled posterior. Maximum height and breadth are medial or slightly anterior of the medial line; maximum length is close to the ventral margin. Internally, the inner margin and line of concrescence do not coincide, with wide anterior and posterior vestibules.

Remarks. This species is assigned to Tasmanocypris? based on the size, general shape, maximum height medially, LV larger than RV, central muscle scars arrangement, and large vestibules. The muscle scar pattern is that of Tasmanocypris and not of Phlyctenophora. Paracypris (emended diagnosis Maddocks 1988) is far less symmetrical in lateral and dorsal

18 view, having the maximum height and breadth well forward of the medial line. Despite the common ancestry and close relationships between these and other genera (McKenzie 1982), there remains much confusion within the family, particularly since most diagnoses were made on soft parts of Recent material and not on fossils (Maddocks 1988). McKenzie’s (1979) original description of Tasmanocypris was based on one Recent species, T. dartnalli McKenzie. Another Recent species was added later, Tasmanocypris dietmarkeyseri (Hartmann 1979). Both of these species have rounded posterior margins. The later inclusion of Tasmanocypris eurylamella McKenzie, Reyment & Reyment introduced a species with a more angled posterior, more similar in appearance to T.? latrobensis than the younger material. This species was most prolific in the stratum believed to be the Turritella Bed.

Measurements. Length ranges from 0.93–1.3 mm, height 0.4–0.5 mm; smaller specimens from sample 47A of length 0.78 and 0.4 mm appear to be the same species.

Material. 18 adult carapaces and valves, plus fragments.

Location and age. Latrobe-1, Dilwyn Formation including Rivernook Member, 299.6 m– 211.23 m; ?latest Paleocene/?earliest Eocene–Early Eocene.

Tasmanocypris? sp. Figs 3J-K; 5L-M

Remarks. The tentative tasmanocypridid identification in preference to Paracypris (emended diagnosis Maddocks 1988) is based on the proportions (maximum height and breadth are medial or very close to medial), the left valve overlap, the adductor muscle scar pattern of two subvertical rows (three anterior scars, two posterior plus an elongate capping scar), and the wide inner lamella and vestibule.

Measurements. LV: (broken), length approx. 0.85 mm, height 0.4 mm. C: length 0.8 mm, height 0.42 mm, breadth 0.4 mm. C: (damaged) length 0.86 mm, height 0.4 mm.

Material. 2 carapaces and 1 valve.

Figured specimens. Fig. 3J, 5L-M (P312769), sample 54B at ~296.5 m; Fig. 3K (P312768) sample 56 Top at 304.8 m.

Location and age. Latrobe-1, Dilwyn Formation, Rivernook Member and Rivernook A Bed, 304.8– ~296.5 m; ?latest Paleocene/?earliest Eocene.

Suborder PODOCOPA Sars 1866 Family BAIRDIIDAE Sars 1888 Neonesidea Maddocks 1969 Neonesidea aff. N. australis (Chapman 1914) Figs 3L-M Affinities Bairdia australis Chapman 1914: 31-32, Pl. 6, fig. 7. Neonesidia [sic.] australis – Whatley & Downing 1983: 351, Pl. 1, figs 5-6. Neonesidea australis – Warne 1987: Appendix. Neonesidea australis – Warne 1988: 16, Figs 9 A-B. Neonesidea australis – McKenzie, Reyment & Reyment 1991: 140, 142, Pl. 1, fig. 5.

Fig. 3.

A-B. Cytherelloidea jugifera McKenzie, Reyment & Reyment 1991. A. ACRV, P312762. B. Juv. LV, P312761.

C-D. Cytherelloidea hrycga? McKenzie, Reyment & Reyment 1993 C. Detail of adductor muscle scars external. D. Juv. LV external, P312790.

E-F. Paracypris sp. E. Damaged LV internal, P312767. F. LV internal adductor muscle scars, P312767.

G-I. Tasmanocypris? latrobensis sp. nov. G. ARV external, P312764. H. ALV external, P312765. I. ALV internal, P312766.

J-K. Tasmanocypris? sp. J. LV internal, P312769. K. CRV external, P312768.

L-M. Neonesidea aff. N. australis (Chapman 1914). L. ACLV, P312770. M. ARV internal, P312771.

N. Cytheralison corrugata? fragment RV, external, P312775.

O. Cytheralison sp. fragment LV, P312778.

P. Kuiperiana sp. cf. K. lindsayi (McKenzie, Reyment & Reyment 1991) ACLV, P312773.

Scale bar = 100 microns except for C, F in which scale bar = 10 microns.

Neonesidea australis – Ayress 1995: Fig 4.1, Tables 1, 3.

Remarks. This species is very similar in outline to Neonesidea australis (Chapman 1914) especially when compared to N. australis of Ayress (1995). Internally, the inner margin of Neonesidea australis in Whatley & Downing (1983) appears to be narrower than Neonesidea aff. N. australis, particularly in the posterior. The most significant difference is in size; this form is considerably smaller than others that range in length from 1.2–1.25 mm (Whatley & Downing 1983; Warne 1988; McKenzie, Reyment & Reyment 1991). Neonesidea aff. N. australis is presumably an ancestor of N. australis. If confirmed as the same species this would extend its range from the previously earliest appearance of Late Oligocene (McKenzie et al. 1991) back to earliest Eocene and possibly Late Paleocene. The fragment from 344.42 m has the characteristic muscle scars of the genus.

Measurements. Length 0.82–0.85 mm, height 0.47–0.58 mm.

Material. Eleven mostly damaged male and female specimens.

Figured specimens. Fig. 3L (P312770); Fig. 3M (P312771). Both from sample 43B at 229.21 m.

Location and age. Latrobe-1, Dilwyn Formation including Rivernook Member and possibly Pember Mudstone, 295.35–211.23 m, possibly also 344.42 m; ?latest Paleocene/?earliest Eocene–Early Eocene.

Family LOXOCONCHIDAE Sars 1925 Kuiperiana Bassiouni 1962 Kuiperiana sp. cf. K. lindsayi McKenzie, Reyment & Reyment 1991 Fig. 3P

Affinities Myrena sp. McKenzie 1979: 93, 94, Pl. 1, fig. 10, p. 100, Fig. 2. Myrena lindsayi McKenzie, Reyment & Reyment 1991: 152, Pl. 4, fig. 4, Pl. 5, fig. 10. Myrena lindsayi – McKenzie, Reyment & Reyment 1993: 89, Pl. 3, figs 4-7. Kuiperiana lindsayi – Majoran 1995: Fig. 3U, Appendix Table. Kuiperiana cf. lindsayi – Ayress 1995: Tables 1, 3, Fig. 8.2. Kuiperiana lindsayi – Majoran 1996: 22, Pl. 1, fig. 3.

Remarks. Kuiperiana is the senior synonym of Myrena Neale (1967; Szczechura 2001). When compared to Kuiperiana lindsayi (McKenzie, Reyment & Reyment 1991) the primary reticulate ornament of Kuiperiana sp. cf. K. lindsayi is more widely spaced and has a longitudinal alignment, there is more secondary reticulation between the murae, and the caudal process is more pronounced. These variant features may be an earlier stage of the taxon's development rather than intraspecific variation, but with only one specimen this cannot be determined. If identification is confirmed, this occurrence would extend K. lindsayi to the earliest Early Eocene.

Measurements. Length 0.42 mm, height 0.25 mm, breadth 0.20 mm.

Material. One carapace.

Figured specimen. Fig. 3P (P312773), sample 54B at ~296.5 m.

Location and age. Latrobe-1 bore, Pember Mudstone, Rivernook Member, ~296,5 m; ?latest Paleocene/?earliest Eocene.

Family LOXOCONCHIDAE Sars 1925 Loxoconcha Sars 1866 Loxoconcha sp. Fig. 4A

Loxoconcha sp. McKenzie, Reyment & Reyment 1991: 152, Pl. 5, fig. 3. Loxoconcha sp. McKenzie, Reyment & Reyment 1993: 89, Pl. 3, fig. 8.

Remarks. Only one left valve fragment, possibly female, was found. Its similarity to Loxoconcha sp. McKenzie, Reyment & Reyment (1993) is more readily apparent than to Loxoconcha sp. McKenzie, Reyment & Reyment (1991), identified as being conspecific. The concentric ornament consists of broad, shallow pits and low murae.

Measurements. Approximate length 0.40 mm, approximate height 0.25 mm.

Material. One fragile left valve, possibly female, broken in handling.

Figured specimen. Fig. 4A (P312772), sample 47A at 262.74 m.

Location and age. Latrobe-1 bore, Dilwyn Formation, Turritella Bed, 262.74 m; Early Eocene.

Family XESTOLEBERIDIDAE Sars 1928 Xestoleberis Sars 1866 Xestoleberis? sp. Fig. 2R

Remarks. No taxonomically identifying features could be observed on this single carapace. The dorsal view is ovate with maximum width just post-medial. Left valve overlaps right. The surface is smooth and unornamented. Normal pore canals are large and evenly spaced. No muscle scars or xestoleberid spot were visible. The identification is based on the overall size, shape, and overlap.

Measurements. Length 0.41 mm, height 0.26 mm, breadth 0.27 mm.

Material. One carapace.

Figured specimen. Fig. 2R (NMV P 312760), sample 54B at ~296.5 m.

Location and age. Latrobe-1 bore, Dilwyn Formation, Rivernook Member, ~296.5m; ?latest Paleocene/?earliest Eocene.

Family BYTHOCYTHERIDAE Sars 1926 Cytheralison Hornibrook 1952 Cytheralison corrugata? McKenzie, Reyment & Reyment 1991 Fig. 3N

Affinity Cytheralison corrugata McKenzie, Reyment & Reyment 1991: 149-150, Pl. 2, figs 11, 15, Pl. 3, fig. 15.

Remarks. The single fragment resembles C. corrugata McKenzie, Reyment & Reyment (1991). This specimen and Cytheralison sp. extend the range for the genus in southeastern Australia to Early Eocene, predating the Late Eocene occurrence in the Browns Creek Clays at Castle Cove (McKenzie et al. 1993). The genus is found in Late Cretaceous rocks of the Carnarvon Basin, Western Australia (Bate 1972).

Measurements. Height 0.36 mm.

Material. One fragment, right valve.

Figured specimen. Fig. 3N (P312775), sample 47B at 264.57 m.

Location and age. Latrobe-1 bore, Dilwyn Formation, Turritella Bed, 264.57 m; Early Eocene.

Cytheralison sp. Fig. 3O

Remarks. This single Cytheralison fragment with its symmetry of concentrically arranged rounded pits matches none yet described.

Measurements. Height 0.35 mm.

Material. One left valve fragment.

Figured specimen. Fig. 3O (P312778), sample 47B at 264.57 m.

Location and age. Latrobe-1 bore, Dilwyn Formation, Turritella Bed, 264.57 m; Early Eocene.

Family PECTOCYTHERIDAE Hanai 1957 Munseyella Van Den Bold 1957 Munseyella dunoona McKenzie, Reyment & Reyment 1993 Fig. 4H

Munseyella dunoona McKenzie, Reyment & Reyment 1993: 96, Pl. 4, figs 7-10. Munseyella dunoona – Majoran 1995: 77, Fig. 3L, Appendix Table. Munseyella dunoona – Ayress 1995: Figs 8.10, 8.11, Tables 1, 3. Munseyella dunoona – Majoran 1996: Table 2, Appendices 1, 2. Munseyella dunoona – Neil 1997: 174, Figs 2H, I.

Remarks. This specimen’s identity was confirmed when compared to specimens of M. dunoona from the Rivernook Member outcrop (Section 3 herein), despite the damage to its carapace.

Measurements. Length 0.35 mm, height 0.20 mm, breadth, 0.16 mm. Length 0.36 mm, height 0.20 mm, breadth mm, 0.16 mm (lost).

Fig. 4.

A. Loxoconcha sp. P312772 damaged LV.

B-E. Neobuntonia taylori sp nov. B. Holotype, RV external detail of “hinge ear” area, P312774. C. Paratype RV internal detail anterior hinge element and possible ocular sinus, P312777. D. Holotype ARV external, P312774. E. Paratype ARV internal, P312777.

F. Echinocythereis karooma McKenzie, Reyment & Reyment 1993, AMRV, P312779.

G. Cletocythereis kurrawa McKenzie, Reyment & Reyment 1993, ACLV, P312781.

H. Munseyella dunoona McKenzie, Reyment & Reyment 1993, ACRV, external, P312780.

I. Echinocythereis karooma McKenzie, Reyment & Reyment 1993, AFRV, P312776.

J. Trachyleberis thomsoni AMRV internal, P312787.

K. Indet. gen. sp. fragment RV, P312782.

L-M. Trachyleberis thomsoni? small form. L. AFLV external, P312784. M. AMRV external, P312785.

N. Trachyleberis thomsoni damaged juv. LV external, P312788.

O. Trachyleberis? sp. ALV external, P312783.

P-Q. Trachyleberis thomsoni large form. P. ALV external, P312789. Q. ALV external, P312786.

Scale bar = 100 microns except for B, C in which scale bar = 10 microns.

Material. Two carapaces, (one lost).

Figured specimen. Fig. 4H (P312780), sample 54A at ~295.96 m.

Location and age. Latrobe-1 bore, Dilwyn Formation, Rivernook Member, ~295.96 m; ?latest Paleocene/?earliest Eocene.

Family HEMICYTHERIDAE Puri 1953 Neobuntonia Hartmann 1981 Neobuntonia taylori sp. nov. Figs 4B-E, 5A-J

Derivation. Named after David J. Taylor, micropalaeontologist, who loaned the author the Latrobe-1 material in which this species was found.

Types. The holotype is an opened carapace (Figs 5C-D drawn prior to opening) with the right valve P312774 being Figs 4B, 4D, (left valve P312791 is not illustrated), Pember Mudstone Member at 313.64 m (58A). Paratype: P312777 (Fig. 4E), upper part of the Rivernook Member 292.3 m (53B).

Diagnosis. A Neobuntonia with maximum length medially, maximum height at hinge ear, caudal process positioned postero-medially, and ornament of punctae that are coarsest in the subcentral area.

Description. The carapace is sub-ovate in lateral view with broadly rounded anterior, the dorsum and ventrum are convex. The posterior margin is sub-rounded in the right valve, and in the left valve is sometimes slightly pointed, it is not expressed as a distinct caudal process. Maximum length medial, maximum height at hinge ear, and maximum width just posterior of mid-length. Carapaces are sub-equal with the left valve overlapping the right, but with the anterior margin of the right valve extending slightly past the left valve. When viewed dorsally the margin is sinuous, with the antero-dorsal area corresponding with the anterior hinge elements markedly intruding upon the right valve. In the medial area of the hinge this encroachment is temporarily reversed (Fig. 5C). This species has a ventral longitudinal ridge corresponding to the alar position; the carapace in sample 58A possessed sharp spines at the posterior termination of this ridge and in its vicinity (Fig. 5D). The antero-dorsal hinge ear is more pronounced in the left valve with a large hemi-spherical surface expression somewhat resembling the appearance of an eye tubercle, but it is caused by the size and depth of the socket for the large anterior hinge element on the right valve. The right valve is not so developed externally in this hinge ear area. Ornament consists of a network of broad pits of various sizes that are larger in the central area and diminish in size anteriorly and posteriorly. The broad, flat murae between the pits form a sub-concentric pattern, the most noticeable alignment is roughly parallel to the dorsal and ventral margins. Anterior and posterior marginal denticles are often present. Internally, the ventral margin is inflexed on both valves. The hinge (Figs 4C, E, 5F) is amphidont. The right valve anterior element is stepped. On the left valve the anterior element is smooth and the bar smooth or possibly very finely crenulated. The right valve rear hinge element is long, narrow and faintly lobed. The inner margin is moderately wide, the vestibule is lacking. Beneath the right valve anterior hinge element is a small cavity which may be an optic sinus, though a corresponding eyespot was not observed (Figs 4C, 5E). Central muscle scars are in a shallow depression, they are difficult to discern but appearing to conform to Neil’s (1994) emended diagnosis for the genus as a sub-vertical row of four elongate adductors. Marginal pore canals are difficult to discern but appear to be simple, straight to slightly curved, and more numerous in the anterior margin

25 than in the posterior. The posterior marginal pore canals are more concentrated in the postero- ventral sector. Normal pores are large and evenly spaced.

Remarks. When Neobuntonia taylori is compared to the only other similar species, N. batesfordiense (Chapman 1910; Museum Victoria P134964, P123366, P123367), N. taylori is larger, differently shaped at the posterior, and has a differing arrangement of the murae/pits. In comparison with figured specimens the following details are noted:  The posterior view of Neobuntonia batesfordiense (Chapman 1910), p. 45, Pl. 8, fig. 36 “end view” redrawn this paper (Fig. 5K) differs from N. taylori (Figs 5H-J).  The caudal process of Neobuntonia taylori is somewhat at variance with N. batesfordiense (Chapman, 1910), N. siebertorum Hartmann (1981, is synonymy of N. batesfordiense) and N. batesfordiense in Neil (1994).  None of the above authors mention or illustrate spines in the vicinity of the ventral ridge, Neobuntonia taylori possesses these in the specimen from 58A but not in 53A, however there can be considerable intraspecific variation in spinosity (Neil 1994).

Hartmann (1981) found Neobuntonia siebertorum (synonym of N. batesfordiense) to be in shallow marine coral reef pools of higher-than-normal salinity. In the Latrobe samples, the glauconite and sulphides suggest a different environment for this species, one of normal salinity from with restricted circulation resulting in reducing conditions (Section 5 herein). The specimens could have been transported post mortem into such an area, but the pristine state of the spines on Neobuntonia taylori from 313.64 m, and the restricted circulation in such an environment would suggest that specimen at least is autochthonous.

This species appears to have been very short ranging, so far only being found in the Rivernook Member and one specimen ~15 m lower in the Pember Mudstone.

Measurements. RV: length 0.82 mm, height 0.46 mm. RV: length 0.73 mm, height 0.45 mm. C: length 0.95 mm, height 0.51 mm, width 0.5 mm. LV: length 0.88 mm, height 0.45 mm.

Material. Six specimens plus several fragments. A single carapace from 313.64 m was opened after preliminary observations and the right valve scanned.

Location and age. Latrobe-1 bore, Dilwyn Formation, Pember Mudstone and Rivernook Member, 313.64–292.3 m; Late Paleocene–?latest Paleocene/?earliest Eocene.

Family TRACHYLEBERIDIDAE Sylvester-Bradley 1948 Sub-family OERTLIELLINAE Liebau 1975 Cletocythereis Swain 1963 Cletocythereis kurrawa McKenzie, Reyment & Reyment 1993 Fig. 4G

Cletocythereis kurrawa McKenzie, Reyment & Reyment 1993: 111, Pl. 7, figs 1-2.

Remarks. In their synonymy McKenzie et al. (1993) list the 1979 citation of Cletocythereis sp. McKenzie, Pl. 2 figs 4, 5. The authors had previously listed this species as Cletocythereis cf. rastromarginata not as Cletocythereis kurrawa. C. cf. C. rastromarginata is more appropriate.

This occurrence extends the range of Cletocythereis kurrawa in southeastern Australia to earlier than the McKenzie et al. (1993) Late Eocene.

Measurements. Length 0.60 mm, height 0.35 mm, breadth 0.275 mm.

Material. One carapace, (scanned), one left valve lost from same sample.

Figured specimen. Fig. 4G (P312781), sample 54A at ~295.96 m.

Location and age. Latrobe-1 bore, Dilwyn Formation, Rivernook Member, ~295.96 m; ?latest Paleocene/?earliest Eocene.

Sub-family ECHINOCYTHEREIDINAE Hazel 1967 Echinocythereis Puri 1954 Echinocythereis karooma McKenzie, Reyment & Reyment 1993 Figs 4F, I

Echinocythereis karooma McKenzie, Reyment & Reyment 1993: 112, Pl. 7, figs 7-8. Echinocythereis karooma – Majoran 1995: Appendix Table. Taracythere karooma (McKenzie, Reyment & Reyment 1993) – Ayress 1995: 918. Echinocythereis karooma – Majoran 1996: 20, P. 1, fig. 9, Tables 1, 2, Text Fig. 6, Appendices 1, 2.

Remarks. The specimens match closely in all details except for having a distinct subcentral tubercle contrasting with the indistinct one in the original description. As the genus description for Echinocythereis corresponds more comprehensively with these specimens, it has been retained in preference to Taracythere Ayress (1995).

Measurements. Average size: length 0.62 mm, height 0.36 mm, breadth 0.33 mm.

Material. Total 16 specimens: 1 C F, 8 LV, 6 RV, 1 fragment.

Figured specimens. Fig. 4F (P312779); Fig. 4I (P312776), both from sample 47B at 264.57 m.

Location and age. Latrobe-1 bore, Dilwyn Formation including Turritella and Trochocyathus beds, 264.57–211.23 m; Early Eocene.

Sub-family TRACHYLEBERIDINAE Sylvester-Bradley 1948 Trachyleberis Brady 1898 Trachyleberis thomsoni Hornibrook 1952 Figs 4J, N, P-Q

Trachyleberis thomsoni Hornibrook 1952: 33, Pl. 3, figs 40, 41, 47. Trachyleberis thomsoni – Ayress 1993: 133, Text Figs 3-5, Pl. 9, Q, R. non Trachyleberis cf. careyi – McKenzie, Reyment & Reyment 1993: 105, Pl. 6, fig. 6. Trachyleberis thomsoni – Majoran 1995: 78, 79, Fig. 3G, Appendix Table p. 80. Trachyleberis thomsoni – Majoran 1996: 20, 21, 22, 24, 27, Pl. 1 fig. 13, Tables 1, 2, Appendices 1, 2. Trachyleberis thomsoni – Majoran 1996: Fig. 9L, Tables 1, 2.

Fig. 5.

A-J. Neobuntonia taylori sp. nov.

A, D. Holotype LV (P312791) and RV (P312774) lateral views. B. Holotype carapace dorsal view prior to opening (valves P312774 and P312791). C. Holotype C ventral view prior to opening (valves P312774 and P312791). E. Holotype, anterior hinge element and optic sinus, RV internal view, P312774. F. Holotype, LV and RV hinge elements, valves P312791 and P312774. G. Central muscle scars. H. Holotype LV posteral view P312791. I. Holotype RV posteral view P312774. J. RVs posteral views.

K. Neobuntonia batesfordiense (after Chapman 1910) posterior view.

L-M. Tasmanocypris? sp. P312769.

L. Adductor muscle scars. M. LV internal view.

Remarks. The ornament ranged from blunt nodose tubercules to sharp bi-, tri- and polyfurcate spines, some almost spatulate. The anterior hinge element is stepped. This large, robust, long- ranging species is found through most of this section. It is noticeably most abundant in the Turritella Bed.

Measurements. Length 0.95–1.1 mm, height 0.48–0.52 mm, breadth 0.5 mm.

Material. 30 specimens.

Figured specimens. Fig. 4J (P312787), sample 54 at 295.35 m; Fig. 4N (P312788) LV juv. sample 46B at 260.6 m; Fig. 4P (P312789), sample 40A at 211.23 m; Fig. 4Q (P312786), sample 40A at 211.23 m).

Location and age. Latrobe-1 bore, Dilwyn Formation, including Pember Mudstone, 329.64 m–211.23 m; Late Paleocene–Early Eocene.

Trachyleberis thomsoni? Hornibrook 1952 Figs 4L-M

Trachyleberis thomsoni Hornibrook 1952: 33, Pl. 3, figs 40, 41, 47. Trachyleberis thomsoni – Ayress 1993: 133, Text Figs 3-5, Pl. 9, Q, R. Trachyleberis thomsoni – Majoran 1995: 78, 79, Fig. 3G, Appendix Table p. 80. Trachyleberis thomsoni – Majoran 1996: 20, 21, 22, 24, 27, Pl. 1 fig. 13, Tables 1, 2, Appendices 1, 2. Trachyleberis thomsoni – Majoran 1996: Fig. 9L, Tables 1, 2.

Remarks. These specimens conform reasonably to Majoran (1995, 1996a, 1996b) and Ayress’ (1993) illustrations, but are much smaller than the New Zealand material (Hornibrook 1952; Ayress 1993). Majoran's (1995, 1996) illustrated specimens ranged in length from 0.94–1.0 mm and width from 0.48–0.52 mm, which is closer in size but still larger than this taxon. The taxonomic issues are discussed in much greater detail in Sections 3 and 8 herein.

Measurements. Length 0.75–0.87 mm, height 0.4–0.44 mm, breadth 0.4 mm.

Material. 11 specimens including 2 carapaces plus fragments, all adult.

Figured specimens. Fig. 4L, LVF external (P312784), sample 45B at 257.84 m; Fig. 4M, RVM external (P312785), sample 43B at 229.21 m.

Location and age. Latrobe-1 bore, Dilwyn Formation including Rivernook Member and Turritella and Trochocyathus beds, ~297–229.21 m; ?latest Paleocene/?earliest Eocene–Early Eocene.

Trachyleberis? sp. Fig. 4O

Remarks. Sub-rectangular with broad, low, and indistinct ribs, sulci and tubercles. Anterior and posterior marginal denticulation is present. There are low ridges, or rows of suppressed nodes concentric to the anterior margin on the anterior lateral surface. There is a low subcentral tubercle. Internally, the central muscle scars are indistinct. The hinge is amphidont with the LV having an anterior socket and smooth postjacent tooth, the bar is smooth, and a

29 long posterior socket is present. The tentative genus identification is based on the above features, and the apparent cluster of barely visible tubercles antero-ventral to the subcentral tubercle (more observable in the unscanned carapace from 43B). This species lacks the overall size, or deep depression behind the spinose anterior margin of Trachyleberis careyi. The specimens display the “blunter” posterior shape of Trachyleberis probesioides Hornibrook (1952) when viewed laterally, and may be that species.

Measurements. LV: length 0.75 mm, height 0.35 mm. C: length 0.8 mm, height 0.35 mm, breadth 0.31 mm.

Material. 1 C, 1 LV.

Figured specimen. Fig. 4O (NMV P 312783), sample 40A at 211.23 m.

Location and age. Latrobe-1 bore, Dilwyn Formation, 229.21–211.23 m; Early Eocene.

Genus Indet. Sp. nov. Fig. 4K

Remarks. No clear taxonomic position has been found for this single, reticulate fragment. The fine network of shallow fossae is roughly concentric about the prominent subcentral tubercle. Behind the anterior marginal denticles is a prominent flat-topped, sharp-edged, anterior marginal ridge. Ventrally, there is part of a longitudinal ridge. There is possibly reduced median ridge in the alignment of the longitudinal murae, but no clear indication of a dorsal ridge. An eye tubercle is possibly present, but the observed external protuberance may only be a hinge tubercle relating to the corresponding anterior hinge tooth socket. Internally, the marginal zone is narrow with the inner margin and line of concrescence coinciding. There are no visible vestibules in the available fragment, this could be indicative of a late stage instar, which would conform to the lack of observable hinge elements apart from the anterior socket. Adductor scars not visible.

Measurements. Height at hinge ear 0.33 mm.

Material. One right valve fragment, possibly late stage juvenile.

Figured specimen. Fig. 4K (P312782), sample 47B at 264.57 m.

Location and age. Latrobe-1 bore, Dilwyn Formation, Turritella Bed, 264.57 m); Early Eocene.

CONCLUSION

The ostracod assemblages from the Latrobe-1 bore are the first to be described from across the Paleocene–Eocene boundary, and from the Early Eocene Rivernook A, Rivernook and Princetown ingressions in the Wangerrip Group/Dilwyn Formation. Two taxa are new, Neobuntonia taylori sp. nov. and Tasmanocypris? latrobensis sp. nov. Some taxa in open nomenclature seem to be new species but there is insufficient material for allocation. The time and geographic range of many taxa in the assemblage have been extended. The data supplements other taxonomic studies (Sections 3, 4 and 8) herein and are the basis for palaeogeographic and palaeoenvironmental interpretations herein(Sections 5, 8 and 9). Techniques developed in the course of this paper are described in Section 10.

REPOSITORY

All types and other specimens E. M. scanned in this paper are deposited in the Museum Victoria with the prefix NMV P.

ACKNOWLEDGEMENTS

Grateful thanks are extended to: John A. Talent and Ruth Mawson of Macquarie University Earth and Planetary Sciences for supervisory guidance, support and editorial comment; Michael Engelbretsen for extensive constructive criticism and SEM operation; David J. Taylor and the Geological Survey of Victoria for loan of material; John V. Neil and an unknown reviewer for invaluable comments on the manuscript, Alan D. Partridge for guidance and Museum Victoria for access to its collections. The comments and recommendations of the referees Michael Ayress, Alan Lord and Mark Warne are deeply appreciated and grateful thanks extended.

APPENDIX

Sampling details. Depth information on most of the samples was available (Taylor pers. comm. 1970), those that were lacking have been estimated based on the available data, usual sampling intervals and positions of adjacent samples. The sample number is followed by the depth in metres, ~ indicates approximate position:

40A = 211.23; 41A = 217.32; 42A = 221.89; 42B = 224.64; 43B = 229.21; 44A = 242.32; 44B = 245.06; 45A = 254.2; 45B = 257.84; 46A = 259.38; 46B = 260.6; Sample 860-2 = 262.13-262.74; 47A = 262.74; 47B = 264.57; 48A = 288.4; 53B = 293.3; 54 = 295.35; 54A ~ 295.96; 54B ~ 296.5; 54C ~ 297; 54E = ~298; 54F ~ 298.7; 55 = 299.62; 55A = ~302; 56 top = 304.8; 56A ~ 305.41; 58A = 313.64; 61A = 329.64; 63A = 339.09; 64 = 344.42.

Appendix 1. Stratigraphy, biostratigraphy and sampling data, Latrobe-1 borehole, Otway Basin, Victoria.

ADDENDUM

Data was missing from the tables as they appeared when published, accordingly slight modifications have been made to this section. Wording has also been modified, and references to the other sections added for clarity and coherence in this thesis.

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STOVER, L.E. & PARTRIDGE, A.D., 1973. Tertiary and Late Cretaceous spores and pollen from the Gippsland Basin, southeastern Australia. Proceedings of the Royal Society of Victoria 85(2), 237-286. SWANSON, K.M., 1969. Some Lower Miocene Ostracoda from the middle Waipara district, New Zealand. Transactions of the Royal Society of New Zealand 7(3), 33-48. SZCZECHURA, J., 2001. Ostracods from the Eocene of Seymour Island, Antarctic Peninsula. Palaeontologia Polonica 60, 157-181. TAYLOR, D.J., 1964. Biostratigraphic log Latrobe No. 1 bore. Geological Survey of Victoria, Unpublished Report, PE990957, Department of Manufacturing and Industry Development, Melbourne, 1-3. TAYLOR, D.J., 1965. Preservation, composition, and significance of Victorian Lower Tertiary ‘Cyclammina faunas’. Proceedings of the Royal Society of Victoria, N. S. 78(2), 143-160. TAYLOR, D.J., 1967. Marine transgressive patterns in Victoria. 39th. Congress of the Australian and New Zealand Association for the Advancement of Science, Section C, Abstracts, A3-A4. TAYLOR, D.J., 1970. Personal comments. These are the unpublished charts and notes that underpin Taylor's foraminiferal zones and publications, in particular Taylor 1964, 1965, 1971. TAYLOR, D.J., 1971. Chapter 10 – Foraminifera and the Cretaceous and Tertiary depositional history. In The Otway Basin of Southeastern Australia, H. Wopfner & J.G. Douglas, eds, Special Bulletin, Geological Surveys of South Australia and Victoria, 217-234. TICKELL, S.J., ABELE, C. & PARKER, G.J., 1993. Palynology of the Eastern Otway Basin. Geological Survey of Victoria, Unpublished Report 1993/18, Department of Primary Industries, Victoria, 1-54. TRESSLER, W.L., 1954. Marine Ostracoda. In Gulf of Mexico, Its Origin, Waters, and Marine Life. Fishery Bulletin 89, 429-437. TRUSWELL, E.M., CHAPRONIERE, G.C.H. & SHAFIK, S., compilers, 1991. Australian Phenerozoic timescales – 10. Cainozoic biostratigraphic chart and explanatory notes. Bureau of Mineral Resources, Geology and Geophysics, Record 1989/40, Canberra, ACT, 1-16 +chart. VAN MORKHOVEN, F.P.C.M., 1963. Post-Palaeozoic Ostracoda, Their Morphology, Taxonomy and Economic Use. Volume 2. Elsevier, Amsterdam, London, New York, 1- 478. WARNE, M.T., 1987. Lithostratigraphical associations of the ostracode fauna in the marine Neogene of the Port Phillip and Western Port Basins, Victoria. In Shallow Tethys 2, The Proceedings of the International Symposium on Shallow Tethys 2, Wagga Wagga, 15-17 September 1986, K.G. McKenzie, ed., A.A. Balkema, Rotterdam, Boston, 435-445. WARNE, M.T., 1988. Neonesidea and Bairdoppilata (Ostracoda) from the Miocene of the Port Phillip and Western Port Basins, Victoria, Australia. Alcheringa 12, 7-26. WHATLEY, R. & DOWNING, S., 1983. Middle Miocene Ostracoda from Victoria, Australia. Revista Española de Micropaleontologia 15(3), 347-407. WOPFNER, H. & DOUGLAS, J. G., 1971. Chapter 1 – Area and regional setting. In The Otway Basin of Southeastern Australia. H. Wopfner & J. G. Douglas, eds, Special Bulletin, Geological Surveys of South Australia and Victoria, Ministry of Development and Mines, South Australia and Ministry of Mines, Victoria, 17-25.

SECTION 3

NEW AND REVISED OSTRACODA (CRUSTACEA) ASSEMBLAGES FROM THE DILWYN FORMATION (LATEST PALEOCENE AND EARLY EOCENE), OTWAY BASIN, VICTORIA

COL EGLINGTON

Department of Earth and Planetary Sciences, Macquarie University, Sydney, NSW 2109, Australia. [email protected]

EGLINGTON, C. New and revised Ostracoda (Crustacean) assemblages from the Dilwyn Formation (Latest Paleocene and Early Eocene), Otway Basin, Victoria.

Key words. Paleogene, Paleocene, Eocene, Ostracoda, Wangerrip Group, Dilwyn Formation, Rivernook Member, Latrobe-1, Otway Basin, Australia.

ABSTRACT

Early Eocene ostracod assemblages from the Rivernook Member of the Dilwyn Formation (Wangerrip Group) were obtained from two locations: one an outcrop, the other subsurface in Latrobe-1 bore. Samples from these sites yielded 33 taxa of which 24 were reinvestigated. Two new “dwarf” varieties, Neonesidea australis var. A and Glencoeleberis? thomsoni var. A, are proposed. Due to marked differences in faunal composition of each of the three substantial Rivernook outcrop assemblages, they could not be bulked together and treated as a single assemblage. Assemblages from the Pember Mudstone, Rivernook and Princetown members, and the Trochocyathus and Turritella beds provided data for palaeoenvironmental interpretation. Assemblage comparisons revealed a high degree of commonality between the Rivernook Member (RMA) and Pebble Point, the South Australian Late Eocene, and Late Eocene New Zealand assemblages. There was a very low degree of commonality when compared with an Eocene Antarctic assemblage. The only other bore to provide Late Paleocene/earliest Eocene ostracods, Heywood-10, had a very small latest Paleocene assemblage in the Pember Mudstone of the Dilwyn Formation. Ostracods from the Rivernook outcrop and Heywood-10 bore are the first from those locations.

PREVIOUS RESEARCH, BACKGROUND AND LOCATION OF PRESENT STUDY

The Paleocene–Eocene Chron 24 interval continues to be a challenging stratigraphic interval due to scarcity of fossiliferous sedimentary material representing this interval within and on the margins of basins, and in deep-sea records (Aubrey 1998). Early Paleogene outcrops in southeastern Australia are scarce. The poor preservation of calcitic microfossils in on-shore cores in the Otway Basin, Victoria, has handicapped workers reconstructing the geological and environmental history of this area. Foraminiferal faunas from the Pebble Point and Rivernook strata have been essential for dating and for lateral correlations of the Pebble Point and Rivernook transgressions/ingressions (Taylor 1964a, 1964b, 1965, 1971; McGowran 1965, 1970, 1991; McGowran et al. 2000). Both events occurred during the breakup of Gondwana and subsequent development of the Australo-Antarctic Gulf (AAG).

To date, the Pebble Point Formation has produced the only Paleocene southeast Australian ostracod assemblage (Neil 1997); Latrobe-1 borehole produced the only subsurface Paleogene

Ostracoda; these were first recorded from the Dilwyn Formation (Eglington 2006; Section 2 herein). Prior to that taxonomic study, there had been no published record of ostracods from the Rivernook Member. Baker (1950) provided a thorough listing of the mineralogical and fossiliferous components of the outcropping unit but made no mention of ostracods. Mitchell and Taylor (1965) extracted ostracods along with foraminiferans so knew of their presence but did not record them in their publication. Both graciously made their ostracod-bearing material available for this study.

The Latrobe-1 borehole study (Eglington 2006; Section 2 herein) was limited to the subsurface section and constrained by the very small size of some of the assemblages. Additional material has made it possible to enlarge the subsurface assemblages, and to extend the research to other locations. This paper describes and discusses Early Eocene ostracod assemblages from the Wangerrip Group/Dilwyn Formation that includes the outcropping Rivernook Member, a small collection from the Pember Mudstone Member in Heywood-10 bore, and provides additional data amending the Latrobe-1 bore study (Eglington 2006; Section 2 herein).

GEOLOGICAL SETTING

Location

The Victorian portion of the Otway Basin (Fig. 1), in which the bores and outcrops are located, was formed as a result of Gondwana rifting. It trends east–west, is approximately 500 km long, extends laterally both on and off shore, and contains thick sequences of Mesozoic and Cenozoic strata. Bores sunk for groundwater are: Heywood-10 (completed in 1960 to a depth of 1634 m), Narawaturk-2 (completed in 1961 to 1685 m), Yangery-1 (completed in 1960 to 1320 m) and Latrobe-1 (completed in 1963 to 626 m). The latter two are about 25 km apart in the Port Campbell Embayment. The Rivernook Member outcrops in coastal exposure between Point Ronald and Point Margaret, southwestern Victoria. It is 4 km S of Princetown and approximately 3.3 km SE of Latrobe-1. Pebble Point lies approximately 3 km SE of Rivernook (Fig. 2). The Latrobe-1 stratigraphy, biostratigraphy and lithology have been discussed previously (Eglington 2006; Section 2 herein) and are summarised in Appendices 1 and 2.

Fig. 1. Locations and structures within the Otway Basin, Victoria (after Wopfner & Douglas 1971).

Fig. 2. Rivernook, Pebble Point and Latrobe-1 borehole, Princetown Area, Otway Basin, Victoria (Eglington 2006).

Age

The Pebble Point Formation has been dated as Early–Late Paleocene (Holdgate & Gallagher 2003) with the Pebble Point Transgression/Ingression (Deighton et al. 1976; McGowran 1991; McGowran et al. 1997, 2004) being late Late Paleocene–Upper L. balmei spore/pollen zone (Arditto 1995, Holdgate & Gallagher 2003, McGowran et al. 2004). The Pember Mudstone Member overlies the Pebble Point Formation and is latest Paleocene to earliest Eocene. The Dilwyn Formation contains the Rivernook A and Rivernook Member. Rivernook A is earliest Early Eocene (Ypresian), planktonic foraminiferal zone P6a and the Rivernook Member/Rivernook Ingression is Early Eocene (Ypresian), upper Chron 24, P6b zone (McGowran et al. 2000; Holdgate & Gallagher 2003).

METHODOLOGY

Sampling

Heywood-10 and Narrawaturk-2 residues and slides were borrowed in 1970/71 from D. J. Taylor and from the Geological Survey, Department of Mines, Victoria. They were rewashed, sieved and re-picked for this study. Most of the Latrobe-1 ostracods were described previously (Eglington 2006; Section 2 herein) but the assemblages were enlarged by re- picking. The Rivernook ostracod specimens are from residues and foraminiferal assemblage slides from the Rivernook Member and Rivernook A Bed outcropping near Princetown, Victoria; they were provided by D. J. Taylor and P. Mitchell in 1970/71. Taylor had used this material to develop his foraminiferal assemblages, facies sequence and zonules (Taylor 1964a, 1964b, 1965, 1970 pers. comm., 1971). The size of the outcrop samples before treatment is not known, but it is presumed that Taylor’s were 200 g as was his custom (Taylor 1964a). The abbreviated sample names, collectors’ notes and material used are as follows:

Collector Sample Collector’s Notes

P. Mitchell RIVIV Princetown Rivernook Member: 17.7 g fine residue (re-picked) plus slide of picked ostracods. D. J. Taylor RIVA Rivernook A “see McGowran 20' below main Rivernook”: 1.44 g residue plus slide of picked by-product fauna. RIVB Rivernook B (main Rivernook Member): slide of picked by- product fauna. RIVMcG Rivernook sampled as per McGowran 1965: slide of picked by- product ostracods and 95.4 g residue (re-picked). Also labeled RIV McG 1965. Unknown RIVMEMPT Rivernook Member, Princetown: slide of picked ostracods.

The statistically most reliable sample was the 95.4 g RIVMcG residue. RIVIV is the next best with both residue (17.7 g) and slide. RIV A had just 1.44 g residue and a picked slide; RIVB and RIVMEMPT consist only of picked slides with no extant residues; the latter sample contained only one specimen – an adult male left valve Cytherella postatypica Eglington (Section 4 herein).

Taxa obtained from the Rivernook outcrop samples were studied in conjunction with those described previously from the Rivernook A and Rivernook Member in Latrobe-1 (Eglington 2006; Section 2 herein). Additional Latrobe-1 specimens were obtained by re-picking residues, supplementing the data previously published (Eglington 2006; Section 2 herein). Distribution of taxa from outcrop samples and comparison with Rivernook A and Rivernook Member assemblages in Latrobe-1 are shown in Table 1.

Processing

The high sulphide content in the old bore cores resulted in destruction of calcitic material during storage over the past 30–40 years. Specimens from subsurface were extracted from 30 core samples collected in 1960s, washed by Taylor soon after that time, then rewashed by the author in 1970, hence have survived reasonably intact. Ten 200 g samples from the Late Paleocene–Early Eocene of Yangery-1 bore were processed with hydrogen peroxide, washed, separated by sieving into course (>1.4 mm), medium (0.3–1.4 mm) and fine (<0.3 mm) fractions, and picked for ostracods.

Images

As the majority of taxa are represented by few specimens, scan electron microscopy (SEM) imaging of uncoated ostracods at low vacuum with backscatter was used for most specimens to avoid the gold coating obscuring subsurface structures only visible in transparent to translucent valves. This process slightly reduced the visual quality of the SEM images.

Foraminiferal faunas

The terms Pebble Point, Rivernook, Trochocyathus and Princetown faunas refer to the biostratigraphic intervals used by Taylor (1964a, 1964b, 1965, 1970 pers. comm., 1971) and McGowran (1965) based on their foraminiferal assemblages and have been retained. When referring to sample-based groups of ostracods or foraminiferans, the term “assemblage” has been applied.

TAPHONOMY

Preservation

Ostracod preservation varied from fragile and corroded to nearly perfect, sometimes within the same sample (particularly so in Latrobe-1 bore assemblages). With dysaerobic conditions present in areas of inhibited circulation and stagnation, preservation of calcitic material, both immediately post-mortem and subsequently, will remain a major factor affecting assemblage integrity. It is not possible to ascertain the overall degree of loss these conditions may have caused. Deterioration within the core material due to sulphides has been discussed previously (Taylor 1965; Eglington 2006; Section 2 herein). Integrity of outcrop sample RIVMcG is high, with 95.4 g residue and preservation of very fine calcitic fragments indicating little or no CaCO3 dissolution in situ.

Contamination

Whereas the location (far from the sole opening into the AAG) and there being no evidence of strong currents or tides, reworking of material is likely to have been localised and minimal. Harris (1965) concluded that the outcropping Rivernook–Turritella beds reflected a period of uninterrupted deposition without erosional stages of removal, or major reworking of the sediments. The subsurface samples are all from core not chips, so contamination during recovery would have been very unlikely.

Articulated:disarticulated

The proportion of articulated to disarticulated valves is noticeably higher in outcrop (RIVB = 86.4%, RIVIV = 31.3%, RIVMcG = 9.1%) than subsurface samples. The average for Rivernook Member subsurface samples is 5.3% articulated, this low proportion is consistent through the entire section, with only one of the 22 samples having a ratio above 15%, (small assemblages were not included in this tally). Samples RIVIV, and in particular the RIVB, are biased by presence of Munseyella, a small, robust, strongly hinged pectocytherid, commonly found articulated.

Adults:juveniles

The value of the indicator for autochthonous fauna, the adult/juvenile ratio, is reduced due to small population sizes. The level of corrosion in some samples suggests that small, thin instars would have been destroyed. Overall, in Latrobe-1, the Rivernook Member had the highest proportion of juveniles with an adult: juvenile ratio of 3:1; strata between the Turritella and Trochocyathus 4:1; Turritella and Princetown each had 10:1. Juveniles were absent in the Rivernook A and Trochocyathus beds samples. In outcrop samples, RIVMcG had 10:1, RIVB 40:1; there were none in RIVIV.

RESULTS

Narrawaturk-2 and Yangery-1 bores

Six samples from the Wangerrip Group (at least 408 m thick) in Narrawaturk-2 were collected, processed and examined by the author in 1970 and found to be bare of ostracods; Taylor (1964c) reported the foraminiferal counts as ranging from poor to nonexistent. Ten samples from the Wangerrip Group (over an interval of 115 m) from Yangery-1 bore were likewise barren of fauna.

Heywood-10 bore

The Pebble Point fauna extends above the Pebble Point Formation into the Dilwyn Formation/Pember Mudstone Member and has been dated as latest Paleocene (GEDISa; Taylor 1964b). Only two of the available Wangerrip Formation samples (Heywood-10 core samples BK-1 and BK-3 located in the Pember Mudstone between 1254–1257 m) contained ostracods, in total seven specimens across three families, four genera and four species:

 CYTHERELLIDAE: Cytherella postatypica (2 specimens); Cytherelloidea jugifera? (3 juvenile specimens).  PECTOCYTHERIDAE: Munseyella dunoona (1 specimen).  PONTOCYPRIDIDAE: Maddocksella sp. (1 specimen).

Munseyella dunoona, Cytherella postatypica and Maddocksella all occur in the Paleocene Pebble Point Formation (Neil 1997; Eglington 2006; Section 2 herein).

Samples Species RIV RIV RIVIV RIVB Sub-total MEMPT McG

Pseudeucythere pseudosubovalis 1 1 Rotundracythere aff. rotunda 1 1 Tasmanocypris sp. 2 1 1 Echinocythereis sp. 1 1 Munseyelle kleithria 10 10 Munseyella adaluma 3 3 Munseyella dunoona 4 4 Munseyella bungoona 3 19 22 Tasmanocypris sp. 1 3 1 4 Cytherelloidea jugifera 2 3 5 Hermanites lungalata? 3 3 Paracypris sp. 1 2 2 “Cythereis” sp. 2 2 Tasmanocypris cf. eurylamella 1 1 Trachyleberis brevicosta major 1 1 Trachyleberis aff. reticulopustulosa 2 2 Glencoeleberis? thomsoni var. A 13 13 Oertliella? sp. 2 3 5 Tasmanocypris? latrobensis 6 1 7 Glencoeleberis? thomsoni large 3 1 5 Incertae sedis gen. and sp. indet. 1 1 Eucythere? sp. 1 1 Neonesidea australis var. A 3 3 Trachyleberis? sp. 1 1 Cytherella pinnata ?1 ?1 Cytherella postatypica 1 4 5

Total specimens per sample 1 43 16 44 105 Total taxa per sample 1 13 9 10

Table 1. Earliest Early Eocene ostracod assemblages from outcropping Rivernook Member, Dilwyn Formation, Otway Basin, Victoria.

Rivernook outcrop

The Rivernook fauna (Taylor 1964a, 1964b, 1965) includes the Rivernook A Bed and the Rivernook Member. No ostracods were found in the outcropping Rivernook A Bed samples provided. Four Rivernook Member samples (Table 1) produced 105 specimens distributed over six families, 14 genera and 26 species. The families represented are Cytherellidae, Paracyprididae, Bairdiidae, Pectocytheridae, Eucytheridae and Trachyleberididae. The most abundant species are Munseyella bungoona (43% of RIVB sample, 20.6% of total specimens for surface samples) and Glencoeleberis? thomsoni var. A (29.5% of RIVMcG, 12.1% of total).

Due to the dramatic differences between them, it would be misleading to treat only the three main Rivernook outcrop ostracod assemblages (RIVMcG, RIVIV and RIVB) as a single entity. Most notably, no species is common to all three (Table 1); only RIVMcG has species in common with the others. There are four Munseyella species and 39 specimens, but three of the species and 36 of the specimens are from the one sample; each assemblage has a different dominant family:

 RIVIV: Cytherellidae 33%, Trachyleberididae 33%, Bairdiidae 17%.  RIVB: Pectocytheridae 82%, all other families 5% or less.  RIVMcG: Trachyleberididae 61%, Paracyprididae 27%.

Latrobe-1 bore

The taxonomy of Latrobe-1 ostracods was detailed previously (Eglington 2006; Section 2 herein); additional material has provided more data requiring some revision of taxonomy, species numbers and distribution; this has strengthened the statistical analyses, assemblage sizes and compositions. Twenty-two samples from Latrobe-1 marine Paleogene section (Appendix 1.) have now produced 411 specimens across 27 taxa; platycopids dominated numerically (65.4%). Cytherella postatypica was the most abundant species, comprising 52.1% of all specimens; it was the dominant species in 13 of the 14 samples in which it occurred, often many times more prolific other taxa. The four most numerous podocopids were Tasmanocypris? latrobensis (7.5%), than Glencoeleberis? thomsoni var. A (5.4%), Echinocythereis karooma (4.1%) and Neonesidea australis var. A (3.6%). Typically numbers for individual species were low with 18 of the 27 species (66.6%) accounting for only 8.3% of the total specimens. The Trochocyathus and Rivernook faunas contained 44.5% and 42.3% respectively of all specimens. The Rivernook fauna was the most diverse with 19 species; the Trochocyathus fauna had 14 species and the Princetown fauna 11 species.

Pebble Point fauna. The Pebble Point fauna extends above the Pebble Point Formation into the Dilwyn Formation/Pember Mudstone Member in Latrobe-1. The ostracod assemblage for the Pebble Point fauna from three samples yielded a total of five specimens (Table 2) distributed across five species, five genera and five families. The families represented are Cytherellidae, Trachyleberididae, Paracyprididae, Hemicytheridae and Cytheropterinae.

Rivernook fauna. The Rivernook foraminiferal fauna (Taylor 1965) incorporating both the Rivernook A Bed and the Rivernook Member occurs in the Latrobe-1 bore. Re-picking and re-examination of samples produced an additional 84 specimens augmenting the 90 of the previous study (Eglington 2006; Section 2 herein). The total yield of the two Rivernook A samples was only five ostracod specimens, none unique to the unit; they are Cytherellidae, Cytherella postatypica and Cytherella sp. and Paracyprididae, Tasmanocypris sp. 1 and Tasmanocypris? latrobensis. Eight of the ten Rivernook Member samples were productive

(Table 2) ; they produced 169 specimens in 19 taxa. The podocopid family Cytherellidae predominates – samples 53B = 93%, 54 = 81%, 54A = 83% and 54B = 72%. The three most abundant species are Cytherella postatypica (62.1%), C. pinnata (6.3%) and Cytherelloidea jugifera (4.6%), followed by the podocopids Neobuntonia taylori (4%) and Glencoeleberis? thomsoni var. A (4%). The specimen counts by species are as follows:

Species Specimens 8 1 6 2–5 3 6–10 2 >10 Total 19 169

Trochocyathus fauna. Re-examination added a further 77 specimens to the 106 previously discussed (Eglington 2006; Section 2 herein). Three of the six samples from 7 m of the

large

var. A var.

latrobensis

sp. 1 sp. ?

K. lindsayi

sp. 1 sp.

sp. 2 sp.

.cf.

sp.

Core Recovery (metres) Position Sample Number Sample thomsoni Glencoeleberis? taylori Neobuntonia postatypica Cytherella Cytherella Tasmanocypris Tasmanocypris jugifera Cytherelloidea Kuiperiana Xestoleberis? kurrawa Cletocythereis dunoona Munseyella pinnata Cytherella

Taylor's (1964) Foraminiferal Foraminiferal (1964) Taylor's Faunas Lithostratigraphy australis Neonesidea Paracypris parageios Pelecocythere thomsoni Glencoeberis? Xestoleberis pseudosubovalis Pseudeucythere Oertliella? hrycga Cytherelloidea Total

~292 292.3 53B 2 26 1 29 296 54 2 1 2 23 1 2 31 ~296 54A 1 1 15 1 1 3 2 2 1 9 36 ~296.5 54B 3 2 1 1 39 1 3 3 1 1 1 1 1 58 ~297 54C 1 1 1 3 ~297.5 54D No marine indicators present ~298.5 54E No marine indicators present ~298.5 54F Rivernook Member Rivernook 3 1 1 5

Rivernook Fauna Rivernook 299.6 55 1 1 2 300-5 983-99' 5 5 Riv. 304.8 56top 2 2 305.4 A Bed 305.4 56A 2 1 3 Sub-total 174 308.5 56B 1 1 313.6 58 A 1 1 2

Intervals of poor core recovery - no fauna found - not to scale

Fauna 329.6 61 A 1 ? 2 Sub-total 5 Core not recovered

Pebble Point Point Pebble

Pember Mudstone Member Mudstone Pember Total 5 6 2 8 109 1 3 3 5 7 8 1 1 1 1 1 2 2 1 12 179

Table 2. Ostracod assemblages for Pebble Point and Rivernook faunas, Latrobe-1 borehole, Otway Basin, Victoria. Stratigraphic section not to scale (revised and amended after Eglington 2006).

Trochocyathus fauna through the Turritella/Trochocyathus beds have ostracod assemblages with 20+ specimens, the lowest position at 264.6 m is the most prolific for the entire bore with 116 specimens (Table 3). The planktonic foraminiferans subsurface are very limited (and absent in outcrop; Taylor 1970 pers. comm.).

Princetown fauna. With re-picking, the specimen count increased from 44 to 50, the assemblage at 229.21 m is still the most productive with Cytherella postatypica the dominant species (Table 3).

Comparisons of Rivernook assemblages. Together the 14 outcrop and borehole samples from the Rivernook A Bed and Rivernook Member provided 279 specimens distributed over nine families 19 genera, and 33 species (Table 4). The families are: Cytherellidae, Paracyprididae, Bairdiidae, Pectocytheridae, Eucytheridae, Hemicytheridae, Loxoconchidae, Xestoleberididae and Trachyleberididae. The Rivernook fauna present in the outcrop but absent from Latrobe-1 bore consists of eight genera and 14 species. The Rivernook samples from the outcrop have a higher proportion of carapaces to single valves and much lower juvenile:adult ratios than in Latrobe-1.

Detailed comparisons of all the assemblages and interpretation of the palaeoenvironment are discussed in Section 5 herein.

large A var.

var. A var.

thomsoni latrobensis thomsoni

? ? ?

sp.

? sp.?

ForaminiferalFauna (Taylor 1964) Stratigraphy(depth in metres) SamplePosition (metres) SampleNumber Neonesideaaustralis Glencoeleberis Paracypris Cytherellapostatypica Cytherella Tasmanocypris Glencoeleberis Cytherelloideajugifera Oertliella Cytherellapinnata Cytherallisoncorrugata Cytheralison Echinocythereiskarooma Trachyleberisbrevicosta major Loxoconcha Trachyleberis?sp. Cytherelloideapraeauricula Total

207.25 211.2 40A 1 1 3 2 1 1 1 10

Prin. Mem 229.2 43B 4 14 6 6 4 1 3 38 ~229.5

PrincetownFauna 245.1 1 1 2 256.03 ~257 Sub-total 50 45A 257.8 45B 2 2 3 1 8

Fauna

Bed 259.4 46A 1 1

Trochocyathus 260.6 46B 5 1 8 2 2 4 22 262-3 860-2' 7 2 9

Trochocyathus 262.7 47A 3 5 7 5 1 5 1 27

Bed

264.6 Turritella 264.6 47B 2 4 3 70 6 1 9 2 5 1 1 11 1 116 289.56 Sub-total 183

10 17 4 105 1 26 15 14 2 13 1 1 17 1 1 2 3 233

Table 3. Ostracod assemblages for Princetown and Trochocyathus faunas, Latrobe-1 borehole, Otway Basin, Victoria. Stratigraphic section not to scale (revised and amended after Eglington 2006).

Rivernook Member Riv. A Outcrop Latrobe-1 Bore

Species

RIV B RIV IV RIV McG RIV MEM PT RIV Sub-total 292.3 295.35 ~295.96 ~296.5 ~297 ~298.5 299.62 299.6304.5 - 304.8 305.41 Sub-total Total

Pseudeucythere pseudosubovalis 1 1 1 1 2 Rotundracythere aff. rotunda 1 1 1 Tasmanocypris sp. 2 1 1 1 Echinocythereis sp. 1 1 1 Munseyella kleithria 10 10 10 Munseyella adaluma 3 3 3 Munseyella dunoona 4 4 1 1 5 Munseyella bungoona 19 3 22 22 Tasmanocypris sp. 1 1 3 4 1 2 3 7 Cytherelloidea jugifera 3 2 5 3 3 1 1 8 13 "Hermanites " lungalata? 3 3 3 Paracypris sp. 1 2 2 1 1 3 "Cythereis " sp. 2 2 2 Tasmanocypris cf. eurylamella 1 1 1 Trachyleberis brevicosta major 1 1 1 Trachyleberis aff. reticulopustulosa 2 2 2 Glencoeleberis thomsoni var. A 13 13 1 1 5 7 20 Oertliella ? sp. 3 2 5 1 1 6 Tasmanocypris ? latrobensis 1 6 7 1 3 1 5 12 Glencoeleberis thomsoni large 1 4 5 1 1 2 1 5 10 Incertae sedis gen. and sp. undet. 1 1 1 Eucythere ? sp. 1 1 1 Neonesidea australis var. A 3 3 2 3 5 8 Trachyleberis ? sp. 1 1 1 Cytherella pinnata 1? 1? 2 9 11 12 Cytherella postatypica. 4 1 5 26 23 15 39 3 2 108 113 Cletocythereis kurrawa 2 2 2 Cytherella sp. 1 1 1 1 4 4 Cytherelloidea hrycga ? 2 2 2 Kuiperiana sp. cf. K. lindsayi 1 1 1 Neobuntonia taylori 2 2 1 1 1 7 7 Xestoleberis ? sp. 1 1 1 1 Xestoleberis sp. 2 1 1 1

Total specimens per sample = 44 16 44 1 105 29 31 36 58 3 5 2 5 2 3 174 279 Total taxa per sample = 10 10 13 1 3 6 10 13 3 3 2 1 1 2

Total taxa = 33 Total specimens = 279

Table 4. Rivernook Member outcrop and Latrobe-1 borehole ostracod assemblages.

Faunal affinities and comparisons with other studies

Late Paleocene Pebble Point fauna. When the Pebble Point Paleocene ostracod assemblage (Neil 1997) is compared to the entire Rivernook Member assemblage, there are 11 genera, 12 species (i.e. 36% of Rivernook species) in common or closely affiliated. With this high level of commonality, Rivernook is a natural successor to the Pebble Point assemblage. Pelecocythere parageios Neil 1997 occurred in Neil’s (1997) assemblage as the sixth most abundant species but, over the entire Latrobe-1 section and Rivernook outcrop, only one fragment was identified as P. parageios? (Eglington 2006).

South Australian Late Eocene. Majoran (1995, 1996a, 1996b, 1996c) described and discussed ostracod assemblages from the South Australian Late Eocene. Of the 50 South Australian genera from the Tortachilla Limestone and the Tuketja, Gull Rock and Perkana Members of the Blanche Point Formation, 13 also occur in Latrobe-1/outcrop Rivernook Member with seven species either conspecific or closely affiliated; they are Cytherelloidea jugifera, Echinocythereis karooma, Glencoeleberis? thomsoni, T. reticulopustulosa, Munseyella dunoona, Kuiperiana lindsayi and Pseudeucythere pseudosubovalis.

New Zealand Late Eocene. Ayress (1995) commented that 56 of his 61 Late Eocene New Zealand outer shelf or upper slope genera were also known in southeastern Australia. When compared to the older Rivernook stratum (with 19 genera), 11 are common to both. They are Cletocythereis, Cytherella, Cytherelloidea, Hermanites?, Kuiperiana, Munseyella, Neonesidea, Paracypris, Pseudeucythere, Trachyleberis and Glencoeleberis?. A further three, Eucythere, Oertliella and Xestoleberis, are tentatively identified in the Rivernook Member. Loxoconcha and Cytheralison are found above the Rivernook Member in the Latrobe-1 Early Eocene. At species level, four of the New Zealand taxa, Kuiperiana cf. lindsayi, Munseyella dunoona, Neonesidea australis and Glencoeleberis? thomsoni, are conspecific or closely related to Rivernook taxa.

Antarctic Eocene. The level of conformity is low between an Eocene Seymour Island, Antarctic Peninsula assemblage (Szczechura, 2001) and the Rivernook Member. This is not surprising given that the locations are on diametrically opposite sides of the Antarctic Block. Only two of the 15 Antarctic genera are present―Kuiperiana and Munseyella―both are wide-ranging genera with small, robust carapaces.

“Dwarf forms”

Steineck & Thomas (1996) described a latest Paleocene mid-bathyl section from Maud Rise in the Southern Ocean within which they identified a catastrophic ostracod turnover of a previously stable population, replaced for approximately 25 ky by a “disaster fauna” containing dwarf forms. This “disaster fauna” was assigned to the Paleocene–Eocene thermal maximum, contemporaneous with a global extinction of deep-sea benthic foraminiferans. The Steineck & Thomas explanation for the dwarf fauna was that, based on the mixture of diminutive and moderate-sized ostracod taxa with thin walls and/or weak calcification, there may have been an inflow of subtropical waters, depleted in oxygen but richer in dissolved CO2 so less favorable for biomineralisation.

Three diminutive taxa, Neonesidea australis var. A, Glencoeleberis? thomsoni var. A and Cytherelloidea jugifera McKenzie et al. 1991, previously found only in Latrobe-1 (Eglington 2006; Section 2 herein) were also found in Rivernook Member outcrop samples; they are almost the same age as the dwarf ostracods of Steineck & Thomas (1996). They occurred in medium to very poorly oxygenated bottom waters in Latrobe-1, and high to very highly oxygenated waters in the outcrop samples (Section 5 herein). Unlike those of Steineck & Thomas (1996), they are robust and well calcified, as are all other taxa not affected by in situ post mortem acid attack. That the small size may be phylogenetic rather than reflecting an environmental response cannot be dismissed. With no evidence that the small taxa have been preceded by larger varieties, it is possible that the dwarf forms are the small, initial stages of newly emerging taxa which, in fluctuating environments, were preferentially selected for earlier maturity and higher reproduction rate over larger size/slower development. This would enable them to exploit the highly variable physico-chemical conditions considered to have been present in the Princetown area of the AAG (Section 5 herein).

Palaeoenvironmental and palaeogeographic interpretations

Based on these results, palaeoenvironment deductions concerning benthic oxygen levels are discussed in Section 5 herein. In Section 8, evidence for an early Leeuwin-style current off the Australian west coast is presented; in Section 9 a Paleocene marine connection between the AAG and Tasman Sea is postulated.

TAXONOMY

The following conventions are used; ~ approximately; C articulated carapace; LV left valve; RV right valve; F female; M male; juv. juvenile; A adult; int. internal; ext. external, CMS central muscle scars; MPC marginal pore canals; NPC normal pore canals.

Order PODOCOPIDA Mueller 1894 Suborder PLATYCOPA Sars 1866 Family CYTHERELLIDAE Sars 1866 Genus Cytherella Jones 1849 Cytherella postatypica Eglington (Section 5 herein) Plate 1A non Cytherella cf. C. pinnata – Neil 1997: 170, Figs 4C. Cytherella sp. cf. C. atypica – Eglington 2006: 93, 94, Figs 2G–N, P.

Remarks. Subsequent to Eglington (2006), additional material has allowed for more extensive comparisons to be made; on that basis, a new species, Cytherella postatypica (Section 4 herein), was described. In Latrobe-1, Cytherella postatypica was the second longest ranging species and by far the most numerous (52.1%); the second most prolific species accounted for only 7.5% of the material. In Latrobe-1, it was the dominant species whenever present―13 of the 22 samples across the four faunas: Pebble Point, Rivernook, Trochocyathus and Princetown. In the Rivernook outcrop samples it was present (and dominant) in two of the four.

Measurements. FRV: length 0.8 mm, height 0.5 mm. FRV: length 0.91 mm, height 0.6 mm. MRV: length 0.98 mm, height 0.58 mm. LV: length 0.95 mm, height 0.61 mm. FC: length 0.8 mm, height 0.5 mm, breadth 0.38 mm.

Material. Approximately 100 specimens.

Occurrence and age. Latrobe-1 bore, Dilwyn Formation including Pember Mudstone from 313.64–211.23 m, Upper L. balmei–M. diversus Zone, Late Paleocene?–Early Eocene; Rivernook Outcrop, Rivernook Formation, Early Eocene. Pebble Point Formation, Late Paleocene, (Neil 1997). Heywood-10 bore, Pember Mudstone Member between 1254–1257 m, Late Paleocene?–Early Eocene.

Family BAIRDIIDAE Sars 1888 Genus Neonesidea Maddocks 1969 Neonesidea australis (Chapman 1914) var. A Plate 1G

Synonymy Neonesidea sp. aff. N. australis – Eglington 2006: 99, 101, Figs 3L–M, Tables 1–2.

Affinities Bairdia australis Chapman 1914: 31, 32, Pl. 6, fig. 7. Neonesidia [sic] australis – Whatley & Downing 1983: 351, Pl. 1, figs 5–6. Neonesidea australis – Warne 1987: 441. Neonesidea australis – Warne 1988: 16, Figs 9A, B. Neonesidea australis – McKenzie, Reyment & Reyment 1991: 140, 142, Pl. 1, fig. 5. Neonesidea australis – Ayress 1995: Fig 4.1, Tables 1, 3.

Remarks. This diminutive variety, previously designated as Neonesidea sp. aff. N. australis

Eglington (2006), was found in three Rivernook Member samples (one outcrop, two subsurface) and in four other Latrobe-1 bore strata (extending to the top of the ostracod- bearing section of the Dilwyn Formation. The two locations (eight samples) yielded 18 adult specimens, with lengths 0.78–0.85 mm, contrasting markedly with lengths previously recorded for Neonesidea australis (Whatley & Downing 1983, 1.2 mm; Warne 1988, 1.19– 1.25 mm; McKenzie et al. 1991, up to 1.21 mm). As there were no identifiable features in this variety other than its size it does not warrant separate species status.

Measurements. LV: length 0.81 mm, height 0.58 mm. LV: length 0.82 mm, height 0.57 mm. C: length 0.78 mm, height 0.51 mm, breadth 0.42 mm.

Material. 18 adult specimens.

Occurrence and age. Rivernook Member, Turritella Bed and Princetown Member, Dilwyn Formation; Early Eocene (Ypresian).

Family PARACYPRIDIDAE Sars 1923 Genus Paracypris Sars 1866 Paracypris sp. 1 Plates 1E, 3C

Remarks. Similar in shape but smaller than the single specimen Paracypris sp. from Latrobe- 1 (Eglington 2006; Section 2 herein). Further comparison is not possible as both specimens are damaged.

Measurements. Length 0.68 mm, height approximately 0.5 mm.

Material. Two adult valves (1 LV, 1 RV).

Occurrence and age. RIVMcG sample; outcropping Rivernook Member, Dilwyn Formation; Early Eocene (Ypresian).

Genus Tasmanocypris McKenzie 1979 Tasmanocypris sp. cf. T. eurylamella McKenzie, Reyment & Reyment 1991 Plate 1F

Remarks. This single, partially infilled specimen of Tasmanocypris cf. T. eurylamella, is smaller and from an appreciably earlier stratum than T. eurylamella McKenzie, Reyment &

Plate 1.

A. Cytherella postatypica Eglington (Section 5 herein) AMLV int.

B. Tasmanocypris? latrobensis, ALV int.

C. Cytherelloidea jugifera McKenzie, Reyment & Reyment 1991, AMCRV.

D. Tasmanocypris sp. 2, LV int.

E. Paracypris sp. 1, ALV int. damaged.

F. Tasmanocypris sp. cf. T. eurylamella, ARV int.

G. Neonesidea australis (Chapman, 1914) var. A, ALV.

H-I. Pseudeucythere pseudosubovalis (Whatley & Downing 1983). H. CLV. I. CRV.

J, L-M. Rotundracythere sp. aff. R. rotundra (Hornibrook 1952), adult. J. LV internal. L. RV external from same individual. M. Ornament detail of RV.

K. Tasmanocypris sp.1, adult LV int.

N-O. Eucythere? sp., CRV. N. SEM O. Light microscope digital photo of same specimen to show ornament.

Scale bar = 100 µ, A- L, N- O. Scale bar = 20 µ, M.

Reyment (1991; Late Oligocene, length 0.97–1.05 mm) but, based on observable features, including the adductor muscle scars, it is very similar. It also appears to be very closely related to the smaller Tasmanocypris sp. of Neil (1997), but comparison of the shape of this RV with his figured LV is difficult due to the asymmetry between paracypridid left and right valves.

Measurements. RV: length 0.91 mm, height 0.41 mm.

Material. One adult right valve.

Occurrence and age. RIVMcG sample, outcropping Rivernook Member, Dilwyn Formation; Early Eocene (Ypresian).

Tasmanocypris sp. 1 Plate 1K

Tasmanocypris sp. Eglington 2006: 99, Figs 3J, K, 5L, M, Tables 1, 2.

Remarks. Tasmanocypris sp. 1 is less highly arched than Tasmanocypris? latrobensis Eglington (2006) and lacks the sharply pointed posterior of that species. As in Tasmanocypris? latrobensis, Tasmanocypris sp. 1 has broad, deep vestibules, and a wide inner margin with numerous large, branching, marginal pore canals. The adductor muscle scars consist of a vertical row of four elongate behind two obliquely angled ones.

Measurements. C: length 0.71 mm, height 0.35 mm, breadth 0.31 mm. RV: length 0.8 mm, height 0.36 mm. LV: length 0.8 mm, height 0.39 mm.

Material. 7 specimens.

Occurrence and age. Rivernook A and Rivernook Member, Latrobe-1; RIVB and RIVMcG samples, outcropping Rivernook Member, Dilwyn Formation; Early Eocene (Ypresian).

Tasmanocypris sp. 2 Plate 1D

Remarks. This is the smallest Tasmanocypris found at this locality. Maximum height is anterior of the midline; posterior rounded in both valves; right valve overlaps left. The inner lamella is broad, with a wide fused zone; anterior vestibule extensive; posterior vestibule narrow. Adductor muscle scars obscured.

Measurements. Length 0.41 mm, height 0.23 mm.

Material. Single adult carapace opened to produce two valves.

Occurrence and age. RIVB sample, outcropping Rivernook Member; Early Eocene (Ypresian).

Tasmanocypris? latrobensis Eglington 2006 Plate 1B

53 non Paracypris siliqua Jones & Hinde 1890; Chapman 1917: 52, Pl. 13 fig. 1. Paracypris sp. Neale 1975: 12, Pl. 1 fig 9. ?Tasmanocypris latrobensis Eglington 2006: 97, 99, Figs 3G–I, Tables1, 2.

Remarks. Identical in shape to previously described Tasmanocypris? latrobensis Eglington (2006) and again displaying two size groupings (Eglington 2006; Section 2 herein). The carapace and one RV are particularly well preserved specimens, sufficiently translucent to allow observation of part of the inner lamella, some marginal pore canals and the adductor muscle scars. Paracypris sp. Neale (1975) from the Late Cretaceous of Western Australia had been misidentified as Paracypris siliqua Jones & Hinde (1890) by Chapman (1917; Neale 1975). Based on comparisons of the size and published illustrations, Tasmanocypris? latrobensis and Paracypris. sp. Neale appear to be conspecific.

Measurements. C: length 1.0 mm, height 0.45 mm, breadth 0.4 mm. LV: length 0.95 mm, height 0.46 mm. LV: damaged, length 0.763 mm. RV: length 0.86 mm, height 0.41 mm. RV: length 0.74 mm, height 0.31 mm.

Material. 38 specimens.

Occurrence and age. Latrobe-1 in Rivernook and Princetown Members, and Turritella Bed, Dilwyn Formation; RIVIV and RIVMcG samples, outcropping Rivernook Member, Dilwyn Formation. Early Eocene (Ypresian).

Family EUCYTHERIDAE Puri 1954 Genus Pseudeucythere Hartmann 1989 Pseudeucythere pseudosubovalis (Whatley & Downing 1983) Plate 1H, I

Eucythere (Rotundracythere) pseudosubovalis Whatley & Downing 1983: 368, Pl. 4, figs 4–6, Table 2. Rotundracythere pseudosubovalis – Warne 1987: Pl. 2, fig. F, Appendix. Pseudeucythere pseudosubovalis – McKenzie, Reyment & Reyment 1991: 150, Pl. 5, figs 1–3, Pl. 11, fig. 7. Pseudeucythere pseudosubovalis – McKenzie, Reyment & Reyment 1993: 88, Pl. 3, fig. 1. Eucythere pseudsubovalis sic. – Majoran 1995: 80. Eucythere pseudsubovalis sic. – Majoran 1996b: Appendix 2.

Remarks. This carapace is only slightly smaller than Pseudeucythere pseudosubovalis Whatley & Downing (1983: length 0.44–0.55 mm) so is possibly a mature adult, although considerably smaller than the range recorded by McKenzie et al. (1991: length 0.53–0.58 mm). When compared with a specimen of Pseudeucythere pseudosubovalis from the Late Eocene Browns Creek Clays at Castle Cove of length 0.6 mm, the Rivernook specimen is much smaller, but it is comparable with respect to carapace shape and normal pore canal frequency. This specimen displays faintly the sub-concentric murae in the antero-ventral area that was illustrated by Whatley & Downing (1983) and McKenzie et al. (1991). The earliest previous occurrence for this species was Middle? Eocene (McKenzie et al. 1993).

Measurements. C: length 0.41 mm, height 0.28 mm, breadth, 0.23 mm.

Material. One carapace.

Occurrence and age. RIVB sample; outcropping Rivernook Member, Dilwyn Formation; Early Eocene (Ypresian).

Genus Rotundracythere Mandelshtam 1960 Rotundracythere sp. aff. R. rotunda (Hornibrook 1952) Plates 1J, L, M, 3D

Affinities Eucythere rotunda Hornibrook 1952: 30, Pl. 2 figs 22, 23, 25. Rotundracythere cf. rotunda – McKenzie, Reyment & Reyment 1993: 88, 89, Pl. 3, fig. 3. Rotundracythere rotunda – Neil 1997: 178, Fig. 6I.

Remarks. Overall shape and reticulation of Rotundracythere sp. aff. Rotundracythere rotunda are very similar to R. cf. rotunda (in McKenzie et al. 1993) and R. rotunda (in Neil 1997); this specimen is slightly larger than theirs. The median sulcus characteristic of Rotundracythere rotunda (Hornibrook 1952) is visible in dorsal view. In lateral view, the dorsum in Hornibrook’s material is more roundly arched, lacking the angularity at the apex, and displaying a gently curving hinge-line in the median element which may be due to sexual dimorphism as noted by McKenzie et al. (1993). The median hinge element is crenulate. The main point of divergence is the inner lamella; Rotundracythere rotunda (in Hornibrook 1952) has a wider fused zone and considerably narrower and shorter anterior vestibule. On this basis, conspecificity is rejected.

Measurements. Length 0.43 mm, height 0.3 mm.

Material. One adult carapace opened to produce two valves, both figured.

Occurrence and age. RIVB sample; outcropping Rivernook Member, Dilwyn Formation; Early Eocene (Ypresian).

Genus Eucythere Brady 1868 Eucythere? sp. Plate 1N, O

Remarks. This limonite-covered specimen, with a sub-pentagonal outline in lateral view, faintly displays a concentric arrangement of broad, shallow pits and low, wide murae, visible only on the right valve. The maximum length and height are approximately medial, the maximum width post median; it is asymmetrical in dorsal view. The ornament of Eucythere? sp. resembles that of Eucythere sp. 2 Neil (1997) but his species has a more rounded tear-drop appearance and a less pointed posterior. Neither the developmental stage nor the gender of this single carapace is evident. Eucythere? sp. lacks the triangular outline in lateral view or the maximum height anteriorly that is diagnostic of the genus Eucythere (Van Morkhoven 1963).

Measurements. C: length 0.42 mm, height 0.36 mm, breadth, 0.22 mm.

Material. One carapace.

Occurrence and age. RIVIV sample; outcropping Rivernook Member, Dilwyn Formation; Early Eocene (Ypresian).

Family PECTOCYTHERIDAE Hanai 1957 Genus Munseyella van den Bold 1957

Munseyella bungoona McKenzie, Reyment & Reyment 1993 Plate 2B, F

Munseyella bungoona McKenzie, Reyment & Reyment 1993: 96, 97, Pl. 4, figs 14–17; Pl. 8, fig. 10. Munseyella sp. cf. M. bungoona – Neil 1997: 174, 176, Figs 2G, 9C.

Remarks. This material ranges from distinctly ornamented with pits and ridges to almost smooth. Identification was confirmed by the size, plump shape, distinctive dorsal view and ornament. In length, this material at 0.39–0.42 mm falls between Neil’s older Late Paleocene Munseyella sp. cf. Munseyella bungoona (0.42–0.44 mm) and the younger Late Eocene type (0.37–0.39 mm), thus bridging the size and age differences between those two assemblages. After comparing these Rivernook specimens with the figured micrographs of Munseyella bungoona McKenzie et al. (1993) and Munseyella sp. cf. M. bungoona Neil (1997), allocation to this species is supported.

Measurements. Adults: length 0.39–0.42 mm, height 0.21–0.22 mm, breadth 0.18–0.2 mm.

Material. Twenty two adults (21 C, 1 RV).

Occurrence and age. RIVB and RIVMcG samples; outcropping Rivernook Member, Dilwyn Formation; Early Eocene (Ypresian).

Munseyella kleithria Neil 1997 Plate 2A

Munseyella kleithria Neil 1997: 172, 174, 176, Figs 2A–C, 9D, E.

Remarks. These specimens are slightly below the average size of Neil’s (1997) specimens. The coarsely reticulate ornament is characteristic for the species.

Measurements. C: length 0.5 mm, height 0.26 mm, breadth 0.21 mm. C: length 0.48 mm, height 0.27 mm, breadth 0.21 mm. C: length 0.42 mm, height 0.23 mm, breadth 0.2 mm. LV: length 0.48 mm, height 0.25 mm.

Material. 10 adults, (7 C, 2 RV, 1 LV).

Occurrence and age. RIVB sample; outcropping Rivernook Member, Dilwyn Formation; Early Eocene (Ypresian).

Munseyella dunoona McKenzie, Reyment & Reyment 1993 Plate 2D

Munseyella dunoona McKenzie, Reyment & Reyment 1993: 96, Pl. 4, figs 7–10. Munseyella dunoona – Neil 1997: 174, Figs 2H, I. Munseyella dunoona – Eglington 2006: 103, Fig. 4H, Tables 1, 2.

Remarks. This material has a distinctive ornament of broad pits, knobs and ridges, as

56 compared to the almost smooth specimen found in the Rivernook Member of Latrobe-1 (Eglington 2006; Section 2 herein), and the figured specimens of McKenzie et al. (1993) and Neil (1997). Carapaces at this location were smaller than those of either McKenzie et al. (1993) or Neil (1997). Normal pore canals were few, large and distinct. Until more specimens are available for comparison this material has not been assigned to a new species.

Measurements. Length 0.33–0.37 mm, height 0.18–0.21 mm, breadth 0.13–0.15 mm.

Material. Five specimens, (3 C, 1 LV).

Occurrence and age. RIVB sample and Latrobe-1 ~296 m; outcropping Rivernook Member, Dilwyn Formation; Early Eocene (Ypresian).

Munseyella adaluma McKenzie, Reyment & Reyment 1993 Plate 2C

Munseyella adaluma McKenzie, Reyment & Reyment 1993: 94, 96, Pl. 4, figs 3–6; Pl. 8, fig. 8. non Munseyella warringa McKenzie, Reyment & Reyment 1993: Pl. 4, fig. 12. Munseyella sp. cf. M. adaluma – Neil 1997: 174, Figs 2D, 8B, D, 10B.

Remarks. Conforms to size and description of the holotype as far as can be observed on closed carapaces. Although Neil’s Munseyella sp. cf. Munseyella adaluma is larger (length 0.41–0.48 mm), his figured specimens have the same pattern of murae and pits as the present material. The McKenzie et al. (1993, Plate 4, fig. 12) specimen labeled Munseyella warringa appears to be M. adaluma. The paratypes which are all together in a well slide and collectively numbered P147470–79 at Museum Victoria were examined and, though labeled Munseyella warringa, all except one are considered to be M. dunoona.

Measurements. C: length 0.40 mm, height 0.2 mm, breadth 0.15 mm. C: length 0.41 mm, height 018 mm, breadth 0.15 mm. C: length 0.35 mm, height 0.2 mm, breadth 0.15 mm.

Material. Three carapaces.

Occurrence and age. RIVB sample; outcropping Rivernook Member, Dilwyn Formation; Early Eocene (Ypresian).

Family THAEROCYTHERIDAE Hazel 1967 Subfamily CYTHEROPTERINAE, Hanai 1957 Genus Pelecocythere Athersuch 1979 Pelecocythere parageios? Neil 1993

Pelecocythere parageios Neil 1997: 186, 188, Figs 1A–G, 3C, E.

Remarks. The single, damaged specimen is the only representative of the taxon to be found in Latrobe-1. There were none from Rivernook outcrop.

Material. One damaged left valve, possibly juvenile.

Occurrence and age. Latrobe-1 bore at 308.46 m, in the Pember Mudstone Member below the Rivernook A bed; Late Paleocene?

Plate 2.

A. Munseyella kleithria Neil 1997, ACLV.

B, E. Munseyella bungoona McKenzie, Reyment & Reyment 1993, ACLV, ACRV.

C. Munseyella adaluma McKenzie, Reyment & Reyment 1993, CLV.

D. Munseyella dunoona McKenzie, Reyment & Reyment 1993, ACRV.

F. Incertae sedis, damaged LV.

G-H. “Cythereis” sp., ARV ext. and int. same specimen.

I. Oertliella? sp., ACLV.

J. Oertliella? sp., juv. damaged LV.

K. “Hermanites” lungalata (McKenzie, Reyment & Reyment 1993), juv. LV.

L. Trachyleberis brevicosta major McKenzie, Reyment & Reyment 1991, ACRV.

M. Trachyleberis reticulopustulosa?, ARV.

N. Glencoeleberis? thomsoni large, AMRV.

O. Glencoeleberis? thomsoni var. AMRV.

P. Trachyleberis? sp. CLV.

Q. Glencoeleberis? thomsoni var. A, ARV.

R. Echinocythereis sp., AFCLV.

Scale bar = 100 µ, E, G-R. Scale bar = 50 µ, A-D, F.

Family TRACHYLEBERIDIDAE Sylvester-Bradley 1948 Subfamily THAEROCYTHERINAE Hazel 1967 Genus Hermanites Puri 1955 “Hermanites” lungalata? McKenzie, Reyment & Reyment 1991 Plate 2K

Affinities Bradleya lungalata McKenzie, Reyment & Reyment 1991: 162, Pl. 6, fig. 8, Pl. 10, figs 9–10. “Bradleya” lungalata – McKenzie, Reyment & Reyment 1993: 113, Pl. 7, fig. 13, Pl. 8, fig. 19. “Hermanites” lungulata [sic.] – Neil 1994: 18–19, Pl. 6, fig. 9–10, Pl. 7, figs 1–2, Pl. 14, fig. 7.

Remarks. “Hermanites” lungalata was originally described from the Oligocene and Early– Middle Miocene (McKenzie et al. 1991) and subsequently from the Late Eocene (McKenzie et al. 1993). Neil’s (1994) remarks regarding his Miocene occurrence (also from southwestern Victoria) include a detailed discussion of the morphologic anomalies of this species. The posterior extremity of “Hermanites” lungalata is more acutely angled than seen here in the more rounded “H.” lungalata?; it is positioned closer to the mid-line.

Measurements. LV juv: length 0.8 mm, height 0.45 mm.

Material. Three specimens, (2 LV juvs, 1 broken LV).

Occurrence and age. RIVMcG sample; outcropping Rivernook Member, Dilwyn Formation; Early Eocene (Ypresian).

Subfamily ECHINOCYTHEREIDINAE Hazel 1967 Genus Echinocythereis Puri 1954 Echinocythereis sp. Plate 2R

Remarks. The overall shape of the carapace and arrangement of the pustulate ornament resemble Echinocythereis karooma McKenzie et al. (1993), but this single specimen has a lower height proportional to its length than is seen in that species; it is inflated behind the anterior margin where E. karooma displays a distinct, crescent-shaped depression. LV overlaps RV. Eye tubercles are present, but in Echinocythereis karooma McKenzie et al. (1993) they were described as absent.

Measurements. C: length 0.74 mm, height 0.38 mm, breadth 0.36 mm.

Material. One adult female carapace.

Occurrence and age. RIVB sample; outcropping Rivernook Member, Dilwyn Formation; Early Eocene (Ypresian).

Subfamily TRACHYLEBERIDINAE Sylvester-Bradley 1948 Genus Oertliella Pokorny 1964 Oertliella? sp. Plates 2I, J

?Oertliella sp. Neil 1997: 182, Figs 5B, D.

Remarks. The three adults all appear to be male. The reticulate patterns are very similar to ?Oertliella sp. Neil (1997). Neil described two carapaces from the Late Paleocene Pebble Point Formation and tentatively assigned them to Oertliella on the basis of external features. No additional information is possible here because the Rivernook valves are disarticulated, damaged, and obscured by infill and limonite coating.

Measurements. C: length 0.79 mm, height 0.4 mm, width 0.32 mm. C: length 0.8 mm, height 0.39 mm, width 0.32 mm (Fig. 4I). RV: length 0.75 mm, height 0.32 mm. LVjuv: length 0.65 mm, height 0.36 mm (Fig. 4J).

Material. Three adults (2 C, 1 RV), 2 juveniles (LV).

Occurrence and age. RIVIV sample; outcropping Rivernook Member, Dilwyn Formation; Early Eocene (Ypresian).

Genus Cythereis Jones 1849 “Cythereis” sp. Plates 2G, H, 3B, I Affinities “Cythereis” sp. McKenzie, Reyment & Reyment 1993: 106, Pl. 6, fig. 9 (non 10). Scepticocythereis sanctivincentis Majoran 1996: 17–20. “Cythereis” sp. Neil 1997:182, Fig. 5E.

Remarks. Though the pattern of reticulation on “Cythereis” sp. resembles that of S. sanctivincentis Majoran (1996), there are several significant differences between the two species, particularly with regard to size and shape. When South Australian Eocene Scepticocythereis sanctivincentis specimens are compared with “Cythereis” sp. Eglington, the postero-ventral spine of the former is lacking and the outline in dorsal view is markedly different (Plate 3A, B). In “Cythereis” sp. Eglington, the antero-ventral margin is not as extended or as pronounced, the anterior margin is not “conspicuously inflated” (Majoran 1996c), the ventral margin less inflexed, and the anterior hinge element stepped, not crenulated. When examined immersed in water, “Cythereis” sp. Eglington, was observed to have a U-shaped frontal scar. The specimen was compared with specimens of Late Eocene “Cythereis” sp. McKenzie, Reyment & Reyment (1993) from Castle Cove but they are probably not conspecific because the latter are smaller and the position of the RV optic sinus relative to the anterior hinge element (Plate 3E-I) is different. The “Cythereis” sp. McKenzie, Reyment & Reyment (1993) is incorrectly numbered 10 in Plate 6 of their publication: it should be fig. 9. Comparing images of “Cythereis” sp. Eglington and the damaged “Cythereis” sp. of Neil (1997) shows them to be very similar in shape and reticulation, differing only in size; they may therefore be conspecific. The length of this adult specimen (0.81 mm) places it between “Cythereis” sp. Neil (1997; 0.76 mm) and “Cythereis” sp. McKenzie et al. (1993; 0.91 mm) with S. sanctivincentis Majoran (1996) the larger at 0.97– 1.15 mm.

Measurements. RV: length 0.81 mm, height 0.39 mm.

Material. Two specimens: 1 adult RV possibly male, 1 juv.

Occurrence and age. RIVMcG sample; outcropping Rivernook Member, Dilwyn Formation; Early Eocene (Ypresian).

Sub-family TRACHYLEBERIDINAE Sylvester-Bradley 1948 Genus Trachyleberis Brady 1898 Trachyleberis brevicosta major McKenzie, Reyment & Reyment 1991 Plate 2L

Trachyleberis brevicosta Hornibrook 1952: 33–34, Pl. 3, figs 44–46. Trachyleberis brevicosta major McKenzie, Reyment & Reyment 1991: 170, Pl. 7, fig. 13, Pl. 8, fig. 11. Trachyleberis brevicosta major McKenzie, Reyment & Reyment 1993: 105, Pl. 6, fig. 7. Trachyleberis aff. thomsoni Hornibrook 1952. Majoran 1996a: 255, Fig. 9K.

Remarks. Comparison of this specimen with figured material from the Victorian Late Eocene (McKenzie et al. 1993), and from across the South Australian Eocene–Oligocene boundary (Majoran 1996a), with regard to agreement in carapace size, shape and distribution of the tubercles, supports their conspecificity. The species was not found in the Late Paleocene Pebble Point location near Rivernook (Neil 1997). The present occurrence extends the range of the subspecies to Early Eocene (Ypresian).

Measurements. MLV: length 0.93 mm, height 0.47 mm.

Material. One adult male LV.

Occurrence and age. RIVMcG sample; outcropping Rivernook Member, Dilwyn Formation; Early Eocene (Ypresian).

Trachyleberis reticulopustulosa? Majoran 1996 Plate 2M

Trachyleberis reticulopustulosa Majoran 1996b: 27, 28, Pl. 2, figs 5–9, Appendices 1, 2. Trachyleberis reticulopustulosa – Majoran 1996a: 255, Fig. 9O, Tables 1, 2.

Remarks. A small, elongate, sub-rectangular trachyleberidid closely resembling Trachyleberis reticulopustulosa Majoran 1996 in shape and arrangement of tubercles, though the overall size of the valve is marginally smaller than the type. In this specimen the tubercles and postero-ventral marginal spines are considerably less developed, and the diagnostic reticulation of Trachyleberis reticulopustulosa is not visible. In these specimens the anterior hinge element is heavily stepped/lobed whereas T. reticulopustulosa is described as having “an almost bifid anterior tooth” (Majoran 1996b). Paucity of specimens hindered unequivocal identification.

Measurements. RV: length 0.6 mm, height 0.3 mm.

Material. Two adult right valves.

Occurrence and age. RIVMcG sample; outcropping Rivernook Member, Dilwyn Formation; Early Eocene (Ypresian).

Plate 3.

A. Scepticocythereis sanctivincentis Majoran 1996, C dorsal view (after Majoran 1996).

B. “Cythereis” sp., RV dorsal.

C. Paracypris sp. RV external.

D. Rotundracythere aff. R. rotunda (Hornibrook 1952), RV internal.

E-I. Anterior hinge elements area, RVs internal, (OS = optic sinus; IM = inner margin).

E-F. Scepticocythereis sanctivincentis Majoran 1996, South Australia, Eocene.

G-H. Scepticocythereis sp. Browns Creek Clays, Castle Cove and Browns Creek, Victoria, Late Eocene.

I. “Cythereis”sp., Rivernook Member outcrop.

Plate 3

A B

D E

F G

H I Trachyleberis? sp. Plate 2P

?Trachyleberis sp. Eglington 2006: 106–107, Fig. 4O, Table 1 .

Remarks. When this specimen and one from Latrobe-1 bore are examined together under low-angle illumination to enhance surface features, the similarity is obvious despite the limonitic coating. Some resemblance in appearance to “Rocaeleberis” sudaustralis McKenzie, Reyment & Reyment (1991) is noted.

Measurements. C: length 0.75 mm, height 0.36 mm, breadth 0.33 mm.

Material. One carapace.

Occurrence and age. RIVB sample; outcropping Rivernook Member, Dilwyn Formation; Early Eocene (Ypresian).

Genus Glencoeleberis Jellinek & Swanson 2003 Glencoeleberis? thomsoni Hornibrook 1952 var. A Plate 2O, Q non Trachyleberis cf. careyi – McKenzie, Reyment & Reyment 1993: 105, Pl. 6, fig. 6. Actinocythereis sp. – Ayress 1993b: Fig. 3 L, Table 1. Trachyleberis thomsoni "small form" – Ayress 1995: Fig. 11.5 Glencoeleberis cf. armata Jellinek & Swanson 2003 – Ayress 2006: 370, Fig. 6L, N-P Trachyleberis thomsoni? – Eglington 2006: 106, Figs 4L, M, Tables 1–2. Glencoeleberis? thomsoni var. A – Eglington (Chapter 3 Taxonomy herein).

Affinities Trachyleberis thomsoni Hornibrook 1952: 33, Pl. 3, figs 40, 41, 47. Trachyleberis thomsoni – Ayress 1993: 133, Text Figs 3–5, Pl. 9, Q, R. Actinocythereis aff. thomsoni – Ayress 1993b: Figs 3 O, P, Text Fig. 5, Table 1. Trachyleberis thomsoni – Ayress 1995: Tables 1, 3, Figs 11.4-5. Trachyleberis thomsoni – Majoran 1995: 78, 79, 80 Fig. 3G. Trachyleberis thomsoni – Majoran 1996a: Fig. 9L, Tables 1, 2. Trachyleberis thomsoni – Majoran 1996b: 20, 21, 22, 24, 27, Pl. 1 fig. 13, Tables 1, 2, Appendices 1, 2. Glencoeleberis? thomsoni var. A – Ayress 2006: 370, Fig. 6G-K, M.

Diagnosis. A trachyleberidid with the same shape, alignment of spines and features as Glencoeleberis? thomsoni (Hornibrook 1952) but of much smaller size.

Description. As with Glencoeleberis? thomsoni (Hornibrook 1952), this trachyleberid has four discernable alignments of tubercles in lateral view; three run laterally along the carapace. They are: the ventral ala row terminating at the posterior with a large, sometimes polyfurcate spine, the curving dorsal row commencing just forward of and above the subcentral tubercle and terminating postero-dorsally with a large spine that may be bi- or polyfurcate, and a curving postero-medial row of four or more tubercles behind the subcentral tubercle. The fourth alignment is a transverse row curving upwards from anterior of the subcentral tubercle to the large, semi-spherical eye tubercle. In most specimens all four rows of tubercles are on slightly raised, weakly defined ribs. MPCs are straight to curving, some with medial thickening.

Remarks. The revised Trachyleberis genus Brandão et al. (2013) retained only 17 species, based on carapace features Trachyleberis thomsoni Hornibrook (1952) was specifically excluded (Section 8 herein). Although there is some similarity between Glencoeleberis? thomsoni and the Glencoeleberis taxa of Jellinek & Swanson (2003) in the alignments of tubercles behind the subcentral tubercle, difficulties are encountered when considering accommodating the various thomsoni taxa within Glencoeleberis, these are: 1. G.? thomsoni lack a distinctive ventral rib, they typically have a ventral row of well-developed, separate tubercles; 2. the four tubercles antero-ventral to the sub-central tubercle are far more aggressively expressed than the Glencoeleberis taxa (Jellinek & Swanson 2003); 3. G.? thomsoni have a curving row of tubercles below the eye tubercle; 4. in the Australian large and small forms both straight and curving marginal pore canals (MPCs) occur, some with medial thickening, the MPCs for Glencoeleberis taxa (Jellinek & Swanson 2003) are straight and simple. In the absence of another, more suitable genus, and awaiting the revue foreshadowed by Brandão et al. (2013), the designation of interrogative Glencoeleberis has therefore been chosen, with reservation.

The designation Glencoeleberis? thomsoni var. A is an acknowledgement of its close relationship to G?. thomsoni but smaller size. In Glencoeleberis? thomsoni var. A the length ranged from 0.75–0.85 mm compared to 0.95–1.3 mm for G?. thomsoni Hornibrook (1952; Ayress 1993, 2006; Majoran 1995, 1996a, 1996b). Trachyleberis specimen Fig. 9K of Majoran (1996a) is not T. thomsoni as labeled; it is T. brevicosta major McKenzie, Reyment & Reyment (1993). The outcropping Rivernook Member specimens (sample RIVMcG) are identical in size and appearance to those from Latrobe-1 where the taxon was found in seven samples ranging from Rivernook Member to Princetown Member. Apart from size, this "dwarf" variety does not otherwise differ from the larger form. Both large and small forms have been found in Middle and Late Eocene New Zealand assemblages (Ayress 1993b, 1995, 2006).

Measurements. Length of adults 0.7–0.85 mm, height 0.43–0.47 mm.

Material. 35 specimens.

Occurrence and age. In Latrobe-1, Rivernook and Princetown Members and Trochocyathus and Turritella beds, Dilwyn Formation; RIVMcG sample, outcropping Rivernook Member, Dilwyn Formation; Early Eocene (Ypresian).

Family INCERTAE SEDIS Genus and Species Indet. Plate 2E

Remarks. The single, damaged, limonite-covered valve with the anterior portion missing has a sub-rectangular outline, straight dorsum, inflexed ventrum and rounded, upwardly curved posterior. There are three broad, longitudinal ribs, the middle one sinuous and intersected by the subcentral tubercle. Internal features damaged and obscured by limonite.

Measurements. Portion of LV: available length 0.6 mm, height 0.4 mm.

Material. One LV fragment.

Occurrence and age. RIVIV sample; outcropping Rivernook Member, Dilwyn Formation; Early Eocene (Ypresian).

CONCLUSION

The additional material has extended our knowledge of the occurrence and range of Ostracoda in the Otway Basin area of the Early Eocene Australo-Antarctic Gulf. Up-section assemblage variations in the Latrobe-1 bore reflect both the changing palaeoenvironment (Section 5 herein) and entry of new taxa. The profound differences between the Rivernook assemblages is noteworthy, reflecting significant variation in bottom conditions―a possible area for future enquiry (Section 5 herein). The occurrence of diminutive forms (especially Neonesidea australis var. A and Glencoeleberis? thomsoni var. A) warrants further probing as regards their range, distribution, relationships to other taxa, and to which environmental factors may have been involved, this has been addressed for Glencoeleberis? thomsoni sensu late in Section 8 herein. Because Otway Basin exposures of Early Eocene strata are so limited, future advances in developing understanding of ostracod evolution and palaeoecology at that time is very much dependent on new groundwater and petroleum-exploration bores with good subsurface sections.

REPOSITORY

All specimens electron microscope scanned for this paper are to be deposited in the Museum Victoria with the prefix NMV P.

ACKNOWLEDGEMENTS

Grateful thanks for extensive supervisory guidance, support and editorial comment are extended to Kelsie Dadd, John A. Talent and Ruth Mawson of Earth and Planetary Sciences, Macquarie University; David J. Taylor, Peter Mitchell and the Geological Survey of Victoria for generous loan of material and data and Michael Engelbretsen, formerly of Earth and Planetary Sciences, Macquarie University for extensive editorial guidance, constructive criticism and assistance with SEM operation. The comments and recommendations of the referees Michael Ayress, Alan Lord and Mark Warne are deeply appreciated and grateful thanks extended.

APPENDIX

Ostracod Age Stratigraphy Depositional Environment Studies Majority sandstones with some silt and claystones and Eglington

shales representing 2006 EARLY repetitious coastal marine transgression/ regression

EOCENE phases

Dilwyn Fm Pember Mudstone Member Sand, silt, and mudstone and shales

LATE WANGERRIP GROUP Siliciclastic sediments, Neil 1997 dominantly transgressive shallow marine

PALEOCENE

Pebble Pt Fm

Appendix 1. Otway Basin stratigraphy for the study area (adapted from Holdgate and Gallagher 2003).

Appendix 2. Stratigraphy, biostratigraphy and sampling data, Latrobe-1 borehole, Otway Basin, Victoria.

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TAYLOR, D. J., 1964b. Biostratigraphic log Heywood No. 10 bore. Unpublished Report 24.11.64, Geological Survey of Victoria, Department of Manufacturing and Industry Development, Melbourne, 1. TAYLOR, D. J., 1964c. Biostratigraphic log Narrawaturk No. 2 bore. Unpublished Report, Geological Survey of Victoria, Department of Manufacturing and Industry Development, Melbourne, 1. TAYLOR, D. J., 1965. Preservation, composition, and significance of Victorian Lower Tertiary ‘Cyclammina faunas’. Proceedings of the Royal Society of Victoria, N. S. 78(2), 143-160. TAYLOR, D. J., 1970. Personal comments. TAYLOR, D. J., 1971. Chapter 10 – Foraminifera and the Cretaceous and Tertiary depositional history. In The Otway Basin of Southeastern Australia, H. Wopfner & J. G. Douglas, eds, Special Bulletin, Geological Surveys of South Australia and Victoria, 217-234. VAN MORKHOVEN, F. P. C. M., 1963. Post-Palaeozoic Ostracoda, Their Morphology, Taxonomy and Economic Use. Volume 2. Elsevier, Amsterdam, London, New York, 1- 478. WARNE, M. T., 1987. Lithostratigraphical associations of the ostracode fauna in the marine Neogene of the Port Phillip and Western Port basins, Victoria, southeastern Australia. In Shallow Tethys 2, The Proceedings of the International Symposium on Shallow Tethys 2, Wagga Wagga, 15-17 September 1986, K. G. McKenzie, ed., A. A. Balkema, Rotterdam, 435-445. WARNE, M. T., 1988. Neonesidea and Bairdoppilata (Ostracoda) from the Miocene of the Port Phillip and Western Port Basins, Victoria, Australia. Alcheringa 12, 7-26. WHATLEY, R. & DOWNING, S., 1983. Middle Miocene Ostracoda from Victoria, Australia. Revista Española de Micropaleontologia 15(3), 347-407. WOPFNER, H. & DOUGLAS, J. G., 1971. Chapter 1 – Area and regional setting. In The Otway Basin of Southeastern Australia. H. Wopfner & J. G. Douglas, eds, Special Bulletin, Geological Surveys of South Australia and Victoria, Ministry of Development and Mines, South Australia and Ministry of Mines, Victoria, 17-25.

SECTION 4

NORMAL AND INVERSE VALVE OVERLAPS BETWEEN AND WITHIN PALEOGENE CYTHERELLA (OSTRACODA) SPECIES, OTWAY BASIN, VICTORIA, AUSTRALIA

COL EGLINGTON

Department of Earth and Planetary Sciences, Macquarie University, Sydney, NSW 2109, Australia. [email protected]

EGLINGTON, C. Normal and inverse valve overlaps between and within Paleogene Cytherella (Ostracoda) species, Otway Basin, Victoria, Australia.

Key words. Otway Basin, Paleogene, Australia, Ostracoda, Cytherella, Inversacytherella, taxonomy, valve overlaps, intraspecific variation.

ABSTRACT

A small group of Cytherella with non-typical valve overlaps (LV>RV) is endemic to the Australian and New Zealand region. Descendants of C. atypica Bate (1972), the ancestral form from the Western Australian Late Cretaceous, migrated into the Australo-Antarctic Gulf. C. postatypica sp. nov., a direct descendant, is found in the Otway Basin from the Late Paleocene to Middle Miocene. It is very similar in appearance to C. pinnata McKenzie et al. (1993), a species with a normal (RV>LV) overlap. Conspecificity was considered but rejected because of small, consistent differences in size, outline in lateral view, extent of overlap, central muscle scars, and shape of juveniles. C. batei sp. nov. and six taxa in open nomenclature are all new left-valve-dominant Cytherella from various Otway Basin localities that range in age from Late Eocene to Early Miocene. Inversacytherella Swanson et al. (2005), erected to accommodate Cytherella with reversed valve overlap, but otherwise morphologically very close to C. postatypica and C. pinnata, and the discovery of C. conturba sp. nov., an Oligocene species in which both left-dominant and right-dominant overlaps are found, are viewed as evidence for invalidity of that supposed new genus.

INTRODUCTION

Research into southern Australian Early Cenozoic ostracods has contributed enormously to recent palaeoecological interpretation and to ostracod taxonomy and evolution (e.g. McKenzie 1974, 1978, 1979, 1983; McKenzie & Guha 1987; McKenzie et al. 1991, 1993; Majoran 1995, 1996a, 1996b, 1997; Neil 1995, 1997; and Eglington 2006; Section 2 herein). Neogene studies include Chapman (1910, 1914, 1926); Chapman et al. (1928); McKenzie (1974, 1978, 1981); McKenzie & Neil (1983); McKenzie & Peypouquet (1984); McKenzie et al. (1990); Warne (1986, 1987, 1988, 1990a, 1990b, 1996, 2002) and Neil (1994, 1995, 1997, 2000, 2002, 2006). In addition, biostratigraphic and zonation studies using foraminiferans and spores/pollens, in particular those constructed by Carter (1964), Taylor (1966, 1971), Ludbrook & Lindsay (1969), McGowran (1970, 1971), Harris (1971) and Ludbrook (1971), have provided the framework for dating and establishing southern Victorian stratigraphic relationships.

Taxonomic quandaries have indicated the need for closer study of Cytherella specimens encountered in Paleogene ostracod assemblages (Eglington, 2006; Section 2 herein), especially forms previously referred to as Cytherella sp. cf. C. atypica Eglington (2006).

Among three new species of Cytherella from the Early Cenozoic of southern Australian is the Oligocene C. conturba sp. nov., with both right and left valve overlaps. This discovery challenges the utility of Inversacytherella Swanson et al. (2005), erected to accommodate left-valve-dominant forms that previously would have been included in Cytherella. The problems are compounded by dearth of (or absence of) information about valve overlaps in species descriptions, lack of illustrations depicting dorsal views, low specimen counts, and specimens from earlier studies having been lost. This has caused difficulty in determining the degree of intraspecific variation for the various species. Among unresolved issues remaining to be addressed are clarification of the identity and diagnosis of C. gullrockensis McKenzie et al. (1991).

Valve overlap reversal has been described in a number of post-Palaeozoic ostracod groups such as Krithe but no attempt is made to separate these into separate genera (Van Morkhoven, 1962; lit comm. Ayress, 2014). Additional examples are seen in Limnocythere, Theriosynoecum, Darwinula, Cyprinotus, Candona, Cyclocypris, Cypridea, Buntonia, Microcythere, Cytheridea subgenus Haplocytheridea and Cytherissa (Van Morkhoven, 1962).

This paper is part of a wider taxonomic and palaeoecologic study of ostracod assemblages from the earliest Early Eocene from both outcrop and boreholes in southern Victoria (Fig 1).

GEOLOGICAL SETTING

Structural geology and location

The Bureau of Mineral Resources first used the term Otway Basin in 1958 to describe the coastal strip between Nelson and Port Phillip Bay. By 1960 the definition was extended to include the currently accepted limits, a trough-like depression running east-west between Lacepede Bay, South Australia and the eastern side of Port Phillip Bay, Victoria. The northern limit is defined by the major steepening of the gravity gradient at the northern edge of the thick Lower Cretaceous/Cenozoic sedimentary rocks, and the eastern limit at the Mornington Peninsula-King Island Basement Ridge (Wopfner & Douglas 1971). The main structural components of the Victorian eastern, onshore area of the basin (Fig. 1) are the Warrnambool and Otway Ranges Highs, and the Port Campbell and Tyrendarra Embayments (Wopfner & Douglas 1971).

Fig. 1. Locations, Otway Basin, Victoria, Australia (after Wopfner & Douglas 1971; McKenzie et al. 1993).

On-shore exploratory drilling in the Otway Basin commenced in 1892 (Wopfner & Douglas 1971) and from the mid-20th century had extended off-shore. Subsurface sections sampled for this study were drilled under government contract; the cores were kept by Geological Survey of Victoria. Logs and some of the unpublished reports prepared by Geological Survey geologists, palynologists and micropalaeontologists have been entered into the GEDIS Borehole System database; authorship of these has not always been recorded. Copies of David Taylor’s sampling logs and foraminiferal reports from 1970/1972 were generously made available by him for this study. These, plus anonymous biostratigraphies from the GEDIS database, are referred to extensively.

Rivernook, Castle Cove and Browns Creek are coastal sites located west of Cape Otway. Narrawaturk-2, Latrobe-1, Yangery-1 and Heywood-10 are groundwater exploration bores located inland respectively 1.5, 1.0, 5 and 20 km from the coast (Fig. 1). The Aire district surface sections at Browns Creek and Castle Cove are on the southwestern margin of the Otway Ranges High. The Rivernook Member outcrop, Narrawaturk-2 and Latrobe-1 bores are within the eastern end of the Port Campbell Embayment between the Warrnambool and Otway Ranges highs. Yangery-1 is on the Warrnambool High and Heywood-10 to the west in the Tyrendarra Embayment (Wopfner & Douglas 1971; Holdgate & Gallagher 2003). Bells Headland and Point Addis Beach are near Torquay, northeast of Cape Otway (Fig. 2).

Fig. 2. Bells Headland and Point Addis Beach, southeastern Victoria, Australia.

Stratigraphy and age

The Latrobe-1 and Rivernook stratigraphies have been discussed in detail elsewhere (Eglington 2006; Sections 2 and 3 herein). Narrawaturk-2, Heywood-10 and Yangery-1 boreholes intercept the Port Campbell Limestone and Gellibrand Marl of the Heytesbury Group, the Narrawaturk Formation and Mepunga Sand Formation of the Nirranda Group and bottom in Dilwyn Formation of the Wangerrip Group. The Castle Cove Cenozoic section commences at the unconformity between the Early Cretaceous and the Johanna River Sand (Early Eocene), followed up-section (see Holdgate and Gallagher 2003) by the Browns Creek Clays (Late Eocene), Castle Cove Limestone (Late Eocene/?Early Oligocene) and Lower Glen Aire Clays (Early Oligocene) (Holdgate & Gallagher 2003). At Browns Creek, two shallow gullies intersect the Late Eocene Browns Creek Clays (Holdgate & Gallagher 2003). Bells Headland and Point Addis Beach marine sequences are in the Jan Juc Formation (Late Oligocene: Holdgate & Gallagher 2003).

Locations and ages for the relevant samples are:

Gellibrand Marl: Narrawaturk-2, 522–526 m, Globigerina euapertura biostratigraphic zone (GEDISc), Late Oligocene (Chaproniere et al. 1996). Yangery-1, 421.5 m, Globoquadrina dehiscens (GEDISd), Early Miocene (Chaproniere et al. 1996). Fishing Point Marl: Castle Cove, Sample OCC9, 113.5 m (99.21 m true thickness) above Early Cretaceous/Eocene unconformity at section base, Late Oligocene (Holdgate & Gallagher 2003). Narrawaturk Formation: Yangery-1, 504.5 m, Subbotina angiporoides (GEDISd), Early Oligocene (Chaproniere et al. 1996). Narrawaturk-2, 556–63 m, Globigerina labiacrassata (GEDIS), Late Early Oligocene (Chaproniere et al. 1996); ~564 m, Subbotina angiporoides (GEDISc), Early Oligocene (Chaproniere et al. 1996). Jan Juc Formation: Australian Museum, McKenzie Collection grid slide labelled “bed of marine clays west of Bells Headland Carter 4” square 2, Torquay district, Faunal Unit 4, Victoriella conoides, P21–P22, Late Oligocene (Chaproniere et al. 1996; Holdgate & Gallagher 2003).

METHODOLOGY

Twenty-six samples were collected from the Castle Cove beach section, 38 from the two Browns Creek coastal gullies and 100 samples encompassing the length of the Yangery-1 bore core. Samples of 200 g were treated with hydrogen peroxide, washed, separated by sieving into course (>1.4 mm), medium (0.3–1.4 mm) and fine (<0.3 mm) fractions, and picked. Taylor’s (1964a, 1964b) Heywood-10 and Narrawaturk-2 bore-core residues and slides, used for his foraminiferal studies (Taylor 1964a, 1964b), were reprocessed with hydrogen peroxide, washed, separated by sieving into course (>1.4 mm), medium (0.3–1.4 mm) and fine (<0.3 mm) fractions and picked. One sample (54.65 g) was from the Narrawaturk Formation. The Latrobe-1 and Heywood-10 sampling plus the Rivernook material provided by Taylor are discussed by Eglington (2006; Sections 2, 3, 6 and 7 herein). Because of the loss of calcitic microfossils from the cores due to sulphides (Taylor 1965; Eglington 2006; Section 2 herein), and because these specimens were extracted so soon after the bores were completed, it is possible that these assemblages are the only surviving ostracod specimens from the older onshore Otway Basin bore cores.

TAPHONOMY

All of the adult cytherellids had moderately thick carapaces. Where there were indications of transport, the larger, overlapping valves were invariably much more numerous than their complementing valves. This is presumed to be due to the robustness of the thicker, bulging margins of the overlapping valves. When present, the thinner-edged valves display chipping and damage exceeding that of the stronger, overlapping valves.

SYSTEMATIC PALAEONTOLOGY

Upon completion of these studies, type and figured specimens will be housed in the Invertebrate Palaeontology Collection of Museum of Victoria, Melbourne. Type and figured

74 specimens use the Museum’s P prefix. Specimens from the McKenzie Collection are currently stored in the Marine Invertebrates Section, Australian Museum, College Street, Sydney, but catalogued in the Palaeontology Section with the number F139027.

The following conventions and abbreviations are used: ~ approximately; > greater than; C articulated carapace; LV left valve; RV right valve; F female; M male; juv. juvenile; A adult; A-1 final stage instar; int. internal; ext. external; CMS central muscle scars; MPC marginal pore canals; NPC normal pore canals. For simplicity, the terms dexter/dextral and sinister/sinistral refer to the larger/dominant valve, dexter/dextral = RV>LV and sinister/sinistral = LV>RV. This classification is based on Hartmann and Puri (1974).

Order PODOCOPIDA Mueller 1894 Suborder PLATYCOPA Sars 1866 Family CYTHERELLIDAE Sars 1866 Inversacytherella Swanson, Jellinek & Malz 2005

Maddocks (1990) cautioned that the prevalent custom in ostracod taxonomy of erecting genera based on a very small number of species, with undue emphasis on only one or very few characteristics, hinders phylogenetic analysis, and implies a much larger difference than may actually exist. As data are compiled, the diagnoses invariably prove inadequate. Cytheropteron/Oculocytheropteron are an example of the second point where allocation relies on the presence or absence of a clearly identifiable ocular area on the carapace as to whether to use Oculocytheropteron Bate (1972) or the more inclusive Cytheropteron Sars (1866) for both sighted and sightless cytheropterine species (Neil 1997). A single feature on which a genus is erected may arise independently or appear and disappear within a population or lineage and therefore may not represent a different species, let alone a different genus. Thus, a single feature is not a true marker for differentiation.

The unwieldiness of such a long-ranging, and ubiquitous genus as Cytherella Jones (1849), invites the introduction of new genera when distinctive features arise. For example, the removal of ornamented species to Cytherelloidea Alexander (1929), introduction of Platella Coryell & Fields (1937) for punctate but otherwise unornamented cytherellids, and more recently, Geelongella McKenzie et al. (1991) for cytherellids possessing a very wide marginal flange.

Swanson, Jellinek & Malz (2005) sought to accommodate cytherellids with a reversed valve ratio (LV > RV) in a new genus, Inversacytherella. The diagnostics are: extreme ovoid shape, a very elongate but typically feather-shaped CMS central muscle scars (CMS) of 24–28 individual scars, and a reverse valve ratio (L>R) (Swanson et al. 2005).

The Australian and New Zealand sinistral forms examined so far, have all exhibited an ovate/sub-ovate to sub-rectangular lateral view. However a well developed ovoid shape is not confined to sinistral Cytherella, as it is also observed in dexters, for example: C. ovata Jones (1849), C. lata Brady (1880), C. sp. Dingle (1981), C. pinnata McKenzie et al. (1993), and C. sp. cf. lata Brady (1880; in Yassini & Jones 1995). With respect to the CMS, Swanson et al. (2005) contrast the 24–28 scars for Inversacytherella with the 12-16 scars of ‘typical’ cytherellids, but Cytherella batei sp. nov. is sinistral with ~21 scars, whereas the conventional ovate dexter C. pinnata McKenzie et al. (1993) has at least 23 scars (Plate 4 figs A–C, G–I). Although Swanson et al. (2005) consider the occurrence of reversed valve ratios common in cytherellids, they list only five species for their new generic grouping. One of the five species they specified was regarded as new, and one, Cytherella gullrockensis McKenzie et al., (1991), questionable (this Taxonomy section below).

Despite the very large number of Cytherella species listed over the past 160 years, Van Morkhoven (1963) stated that the right valve was always larger than the left. The first such example of opposite overlap (and so far the earliest geologically) was not recorded until 1972 when the Late Cretaceous form, Cytherella atypica Bate (1972), was found in the Carnarvon Basin of Western Australia. This species was not mentioned by Swanson et al. (2005) but would, on their diagnosis, qualify for Inversacytherella. One of the re-ascribed species is Cytherella gullrockensis McKenzie et al. (1991) from southeastern Australia. Neil (2006) discussed diagnosis and identification issues associated with this taxon and noted, but did not adopt, the new genus Inversacytherella. Issues with Cytherella gullrockensis are discussed in the Taxonomy section herein.

Van Morkhoven (1962) provided examples of post-Palaeozoic ostracod genera containing species with hinge structure reversal relative to the majority of the species (Krithe, Limnocythere, Theriosynoecum, Darwinula, Cyprinotus, Candona, Cyclocypris, Cypridea, Buntonia, Microcythere, Cytheridea subgenus Haplocytheridea and Cytherissa). Swanson et al. (2005) acknowledged the controversy surrounding the separation of species solely on the basis of reversed valve ratios, given that left or right forms are accommodated within the species concept (Triebel & Malz 1969 in Swanson et al. 2005).

Cytherella postatypica and C. pinnata are very similar in appearance, so much so that the author considered the possibility that they were one species despite possessing opposite valve overlaps. This idea was discarded because of small, but consistent differences (discussed in Taxonomy section, Cytherella postatypica).

The critical, and what appeared to be the unassailable diagnostic feature, reversed valve ratio, is now challenged. Triebel & Malz (1969) describe two podocopid species (Loxoconchissa) within which are mixtures of normal and reverse carapaces. They did not consider it to be taxonomically significant, but Malz (Swanson et al. 2005) applied the criterion of valve reversal to support erection of Inversacytherella. Cytherella conturba sp. nov., a Cytherella species displaying both dextral and sinistral carapaces, is a platycopid example of just this phenomenon.

The dilemma often facing palaeontologists is that taxonomic ‘splitting’ will obscure otherwise close relationships. From these examples, and based on taxa discussed in this research, it would appear that a reversed valve-ratio alone is insufficient for taxonomic division at genus level in Cytherella. At species-level it may be diagnostic for most Cytherella, provided there are other differentiating features to support such a decision. C. conturba sp. nov. demonstrates that there is at least one taxon for which the presence of both valve overlaps is intraspecific, hence of no higher taxonomic value in at least one species.

There are two explanations for consideration:

1. Given that these sinistral cytherellids appear to have originated in, and spread from, the Australian marine environment, they may have been genetically labile, appearing and disappearing in different locations with several closely related dextral species possessing the same recessive gene/s.

2. The valve overlap may be a phenotypic phenomenon triggered by environmental influences. If so, dextral and sinistral forms should be identical, or virtually so, however such influences may have affected other features such as size and shape, thus presenting a range of variations giving the appearance of separate species.

Cytherella Jones 1849 Cytherella pinnata McKenzie, Reyment & Reyment 1993 Plates 1A–I, 2Q, 4A–C

Cytherella pinnata McKenzie, Reyment & Reyment 1993: 78, Pl. 1, figs 1, 2. Cytherella cf. C. pinnata – Neil 1997: 170, Fig. 9F. Cytherella pinnata – Eglington 2006: 94–95, Figs 2A–F, Tables 1, 2.

Diagnosis. McKenzie et al. (1993) describes Cytherella pinnata as “a large, compressed, and sub-rotund Cytherella with a feather-like cluster of many adductor scars, trending obliquely backwards, located medially in adults but posteriorly in juveniles”.

Remarks. Rather than consistently showing a “barely discernable inflexure” (McKenzie et al. 1993), the ventral margin of Cytherella pinnata adults may often be straight and occasionally slightly convex, particularly so in right valves where the bulging outer margin and flange of the central ventrum is convex. The ventrum is usually straight to convex in juveniles. In this study, Cytherella postatypica sp. nov. (previously C. sp. cf. C. atypica Eglington 2006; Section 2 herein) was found at both Castle Cove and Browns Creek, but the only Cytherella recorded by McKenzie et al. (1993) for these locations were C. pinnata and C. aff. bellsi. It is possible that Cytherella postatypica was included in the C. pinnata assemblages but, because of its similar appearance, was overlooked. In most mixed assemblages, Cytherella pinnata is larger than C. postatypica.

Cytherella pinnata and C. postatypica were compared with respect to their valve overlaps by Eglington (2006; Section 2 herein). McKenzie et al. (1993) regarded the CMS of Cytherella pinnata as sufficiently distinctive as to render the species easily recognisable and to differentiate it clearly from C. bellsi and C. gullrockensis (McKenzie et al. 1991), but there are no illustrations with which to make these or other comparisons. When Cytherella pinnata is compared to C. postatypica sp. nov., their CMS are of comparable size, position and configuration (Plate 4A–C, G–I). In lateral view their outlines are very similar, both possessing the asymmetry between left and right valves (as the larger accommodates the smaller). Although the two taxa are close to mirror images of each other when viewed together, the larger RV of Cytherella pinnata always has a more robust, bulging outer marginal rim than the larger LV of C. postatypica.

In this species, right valves, especially in adults, are invariably better preserved than left valves due to the strong, thick, overlapping margins. Adult left valves are much less numerous and almost always have worn, chipped edges.

Cytherella pinnata was found in the Rivernook Member subsurface (Eglington, 2006; Section 2 herein), but in outcrop there was only one specimen of questionable identity. New locations are recorded in the Mepunga and Narrawaturk Formations.

Measurements. Length ranges from 0.90–1.18 mm. Sizes for Cytherella pinnata appear to be consistent throughout the section at each location, and vary slightly between sites. At Narrawaturk-2 the size range is 1.0–1.18 mm, Browns Creek, 1.00–1.17 mm, Latrobe-10, 0.9–0.92 mm, and in the Yangery-1 bore 0.94–1.05 mm.

Occurrences and age.  Pebble Point Formation: Late Paleocene (Neil 1997).

 Dilwyn Formation: Latrobe-1: Early Eocene (Eglington 2006; Section 2 herein).  Mepunga Formation: Narrawaturk-2: Faunal Unit 2 (Taylor, 1964), Late Eocene (GEDISc; Chaproniere et al. 1996).  Browns Creek Clays: Browns Creek: P15–P17 (foraminiferal zones), Late Eocene (Holdgate & Gallagher 2003).  Castle Cove Limestone: Castle Cove: Late Eocene/Early Oligocene? (Holdgate & Gallagher 2003).  Narrawaturk Formation: Narrawaturk-2: Faunal Units 3 & 4 (Taylor 1964), Late Eocene/Early Oligocene–Oligocene (Taylor 1964), Yangery-1, Subbotina angiporoides biozone, Early Oligocene (GEDISd; Chaproniere et al. 1996).  Clifton Formation: Narrawaturk-2: Faunal Units 4 & 5 (Taylor 1964), Oligocene-early Early Miocene (Taylor 1964; GEDISc; Chaproniere et al. 1996).  Port Campbell Limestone: Heywood-10: Orbulina suturalis biozone, Middle Miocene (GEDISa; Chaproniere et al. 1996).

Range. Late Paleocene–Middle Miocene.

Cytherella atypica Bate 1972 Plate 2A–C

Cytherella atypica Bate 1972: 4, Pl. 3, figs 1–4, Text Figs 2A, 2B, 2D, 3F.

Affinity Cytherella cf. atypica – Damotte 1992: 825, Pl. 1.1, Tables 2, 3.

Description. Cytherella atypica Bate (1972) is a smooth, oval, moderately sized (length 0.79– 0.85 mm), sexually dimorphic Cytherella. Unfortunately CMS are not visible in the type specimens.

Remarks. Cytherella atypica was part of prolific Late Cretaceous assemblages from the Toolonga Calcilutite, Carnarvon Basin, Western Australia described by Bate (1972). He remarked that the larger left valve was “unlike any previously described Cytherella and atypical for the genus as a whole” (Bate 1972). The types were borrowed from the Natural History Museum, London for this study and rescanned.

Damotte (1992) found Cytherella. cf. atypica in six samples from two Ocean Drilling Program cores on the Exmouth Plateau off the northwest coast of Western Australia dated Campanian and ?Campanian (Damotte 1992). They ranged in size from 0.8–0.96 mm (Damotte 1992). This location places the taxon approximately 300 km off the northwest coast of Western Australia, west of the Carnarvon Basin where Bate found Cytherella atypica.

Overall similarities in size, shape and LV>RV indicate close relationship between Cytherella atypica, C. postatypica sp. nov., C. batei sp. nov. and C. conturba sp. nov. C. atypica is ancestral to the lineage of these left-valve-dominant cytherellids; migration routes can be traced using them as markers (Section 9 herein).

Measurements. Length 0.79–0.85 mm, height 0.50–0.59 mm, width 0.33–0.4 mm (Bate 1972).

Occurrence and age. Toolonga Calcilutite, Carnarvon Basin, Western Australia; Campanian (Bate 1972).

Cytherella gullrockensis McKenzie, Reyment & Reyment 1991

Affinities. Cytherella sp. McKenzie 1979: 96, Pl, 1, figs 3–4. Cytherella sp. Whatley & Downing 1983: 385, Pl. 8, figs 6–8. Cytherella gullrockensis McKenzie, Reyment & Reyment 1991:137–138, Pl. 1, figs 2, 4. Cytherella aff. gullrockensis – Majoran 1995: 78, Appendix Table. Cytherella gullrockensis – Majoran 1995: 78, 79, Fig. 3D, Appendix. Cytherella gullrockensis – Majoran 1996b: 20, 22, Pl. 1.fig. 1, Text Fig. 6, Table 1, Appendix 1, 2. non Cytherella cf. C. pinnata – Neil 1997: 170, Figs 4C. [C. postatypica Eglington this section herein] Cytherella gullrockensis – Swanson, Jellinek & Malz 2005: 181. Cytherella sp. cf. C. gullrockensis – Neil 2006: 37-38, Fig. 2C.

Remarks. Neil (2006) noted inconsistencies between Cytherella gullrockensis McKenzie, Reyment & Reyment’s (1991) description and illustrations and was hesitant to confirm conspecificity for his Cytherella sp. cf. C. gullrockensis. The McKenzie et al. (1991) diagnosis, description and comparative information are fairly general and subjective so, without additional accompanying illustrations, do not discriminate sufficiently now that more assemblages with comparable taxa have been encountered. McKenzie et al. (1991) do not mention C. gullrockensis having an atypical valve relationship though their figured specimen (FCRV, Plate 1, fig. 4 in McKenzie et al. 1991) clearly displays a LV>RV overlap. The only mention by McKenzie et al. (1991, 1993) of valve ratios for the cytherellids (Cytherella pinnata, C. gullrockensis, C. sp., C. bellsi and C. aff. bellsi) is of C. pinnata having the normal RV>LV (as does C. aff. bellsi according to their illustration). Lacking supporting evidence for RV or LV dominance, and with the discovery of new sinistral Cytherella species of similar appearance to dextral taxa, the possibility exists that the original assemblage described as C. gullrockensis contained a mix of specimens/taxa with dextral and sinistral forms.

McKenzie et al. (1991) identified McKenzie’s (1979) Cytherella sp. in the Late Eocene of the Willunga Embayment, South Australia, as C. gullrockensis but, to confirm this, they must have the same valve relationships. From its size, and shape, McKenzie’s (1979) Plate 1, fig. 3 LV appears to be a juvenile.

Majoran (1995, 1996b) illustrated Cytherella gullrockensis from the Gull Rock and Tuketja Members, both Late Eocene Blanche Point Formation, South Australia. Though in lateral view, the two FLVs (1995, 1996b) are dissimilar in outline, the Majoran (1995) illustration is more uniformly ovate with a medially arching dorsum. The Majoran (1996) illustration is highest behind the median and descends steeply to the mid-posterior. The FLV Cytherella gullrockensis (Majoran 1995) appears from the angularity of its anterior margin (evenly curved in C. gullrockensis) to be a RV, but close examination of the image indicates it has the correct CMS orientation for a LV external view; the apparent margin-angularity may be distortion caused by oblique specimen orientation. Cytherella gullrockensis Majoran (1995) appears to match the general shape illustrated by McKenzie et al. (1991) though it is considerably smaller (L= 0.84 mm compared to 0.92–1.0 mm for mature females) so may be a precocious last-stage juvenile female. Cytherella gullrockensis FLV (Majoran 1996b) of length 0.98 mm is within the range for adult C. gullrockensis but has a markedly convex ventral margin which does not accord with the original description for C. gullrockensis as having “ventrum weakly inflexed”.

Plate 1.

A-I. Cytherella pinnata McKenzie, Reyment & Reyment, 1993. A. FRV, Browns Creek Clays, Browns Creek. B. MRV, Browns Creek Clays, Browns Creek. C. FC, dorsal, Browns Creek Clays, Browns Creek. D. FLV, Browns Creek Clays, Browns Creek. E. MLV, Browns Creek Clays, Browns Creek. F. MLV, Browns Creek Clays, Browns Creek. G. FLV internal, Rivernook Member, Latrobe-1, 295.96 m. H. MCLV, Rivernook Member, Latrobe-1, 295.96 m. I. FRV, internal, Turritella Bed, Latrobe-1, 262.7 m.

J-O. Cytherella postatypica sp. nov, Latrobe-1. J. FC, paratype, dorsal, Princetown Member, Latrobe-1, 229.21 m. K. FRV, paratype, Dilwyn Formation, Latrobe-1, 260.6 m. L. MLV, paratype, Rivernook Member, Latrobe-1, 295.35 m. M. FRV, holotype P312757, internal, Dilwyn Formation, Latrobe-1, 260.6 m. N. MLV, paratype P312758, internal, Rivernook Member, Latrobe-1, 295.4 m. O. FCRV, paratype P312759, Princetown Member, Latrobe-1, 229.21 m.

Scale bar = 100 µ.

Majoran’s two figured specimens are the only illustrations of adult FLVs from the type formation; if correctly identified this would support the observations made by Neil (2006) concerning inadequacy/discrepancy in the original description. Neil (2006) suggested that Cytherella sp. McKenzie et al. (1991) Pl. 1 fig. 8 (in McKenzie et al. 1991), designated by them to be an MLV, is possibly C. gullrockensis FLV. If compared to Majoran’s two FLVs (1995, 1996b), and presuming Majoran’s identification is correct, this seems unlikely as C. sp. McKenzie et al. (1991) is considerably more elongate, and has a very conspicuously inflexed ventral margin. Available South Australian Eocene ostracod assemblages were examined but no sinistral Cytherella were found.

Inability to study type or topotype specimens from the McKenzie et al. (1991, 1993) studies has frustrated clarification. The types, mounted on stubs, were sent by the authors to Uppsala Universitet, Uppsala, Sweden and are currently reported as damaged. Digital photos of the stubs did not show any extant specimens related to this study. An incomplete set of specimens (no paratypes) was provided to the Museum Victoria but does not include Cytherella gullrockensis. The McKenzie private collection, donated to the Australian Museum, College Street, Sydney, was inspected but is incomplete; many slides are unlabeled, others lack cover slips so specimens are lost, damaged or mixed. No specimens that could be assigned to C. gullrockensis have been identified so far from this material. With the possibility that the types have not survived, the most appropriate course of action would be to resample the type locality in South Australia (Blanche Point Formation, Gull Rock Member) and assign neotypes for Cytherella gullrockensis with emended diagnosis, description, and more extensive illustrations.

In order to avoid further confusion the author declines to verify or ascribe any taxa to Cytherella gullrockensis until either original material is located or re-sampling carried out.

Measurements. Length: males 0.89–0.90 mm, females 0.92–1.00 mm (McKenzie et al. 1991).

Occurrence and age. Until identification of Cytherella gullrockensis and synonymy is resolved, its range is taken to be restricted to the Late Eocene Blanche Point Formation, Gull Rock Member, South Australia (McKenzie 1979; McKenzie et al. 1991; Majoran 1995, 1996b).

Cytherella postatypica sp. nov. Plates 1J–O, 2J, P, 4F–I non Cytherella cf. C. pinnata – Neil 1997: Fig. 4C. Cytherella sp. cf. C. atypica – Eglington 2006: 93–4, Figs 2G–N, P.

Derivation. From the Latin post = after, behind. The species Cytherella postatypica sp. nov. appears after but is closely related to C. atypica Bate, 1972.

Holotype. Plate 1M, adult female right valve, P312757, Dilwyn Formation, Latrobe-1 bore, 260.6 m.

Paratypes. Plates 1J–L, N–O, 2J, P, 4F–I. Plate 1N adult male left valve P312758, Plate 1O adult female carapace P312759, Plate 2P juvenile right valve.

Diagnosis. A smooth, moderately large, sub-ovate Cytherella, angled arched dorsum with maximum height medial, left valve overlaps right, female and male carapaces sub-ovate in dorsal view, sexually dimorphic.

Description. A smooth, moderately large Cytherella, a sub-ovate outline in lateral view with an arched dorsum. In external lateral view, all margins are convex; the anterior margin is evenly curved, rising to an arched dorsum with maximum height at the median, then descending to the postero-ventral area; ventrum slightly convex. Maximum length medial. In dorsal view both male and female carapaces are sub-ovate with maximum breadth behind the midline; in females this is approximately one third of the total length from the posterior margin; in males it is farther forward. From the curved area of maximum breadth, the lateral surfaces are somewhat flattened as they descend to the anterior and posterior margins with no further flattening out at the margins apart from a very slight posterior protrusion. For most of the margin the larger left valve overlaps and bulges over the smaller except for the anterior where the margin is retracted outwards so that the marginal areas on the inside edges of both valves are visible. At the anterior, the left valve extends only slightly forward of the right valve. Sexually dimorphic, adult females possess twin posterior brood chambers that inflate the rear portion of the carapace, resulting in a more truncated appearance at the posterior than for the males. In males, the carapace swells markedly laterally at approximately halfway between the midline and posterior margin. A-1 juveniles also display sexual dimorphism.

Internally, the ventrum may be convex to very weakly inflexed medially. The valve margins are appropriately grooved and ridged to accommodate each other except anteriorly where both valves step down from a raised internal rim to the outer valve edge. There is slight thickening in the CMS area, which is situated half way along the valve and predominantly above the midline; this is not reflected in any external surface expression. The CMS details were difficult to see regardless of quality of preservation. They are pinnate biserial, angled obliquely towards the postero-ventral area. There are approximately 13 or 14 scars in the anterior column and approximately 12 in the posterior. The only specimen with clearly discernable CMS was an FRV from Browns Creek which, due to its small size (length 0.86 mm, height 0.56 mm) is most probably an A-1 instar as the adults from this assemblage were often >1.00 mm.

Remarks. Cytherella atypica Bate (1972) has a very regular, is ovate/sub-rectangular outline in lateral view with its dorsal margin more evenly curved than C. postatypica sp. nov. which peaks medially and descends more steeply to the postero-dorsal area. In dorsal view, the margin of the left valve of C. atypica is wider and more robust than the narrow, fine overlap of C. postatypica.

Cytherella postatypica sp. nov. with its arched dorsum is less uniformly ovate/sub-rectangular than C. batei sp. nov.; the lateral surfaces of C. postatypica descend evenly to the margins with no levelling off to form a flatter rim; it ovate in dorsal view for all male and female forms.

To date Cytherella conturba sp. nov. is the only cytherellid species with both dextral and sinistral valve overlaps. Consideration was given to the possibility that because of close similarities in shape, CMS, geographic occurrence and age, Cytherella postatypica and C. pinnata McKenzie, Reyment & Reyment (1993) were also intraspecific variants. They frequently occur together and have done so from the Late Paleocene (Neil 1997; Eglington 2006; Section 2 herein) to the Middle Miocene. This suggestion was rejected for the following reasons:

 The lateral views are dissimilar in several ways: adult males of Cytherella pinnata can be inflexed ventrally; they never are in C. postatypica; the latter section of the C. pinnata dorsum descends posteriorly much more steeply than in C. postatypica; C. pinnata juveniles have an angular posterior margin medially resulting in a more triangular shape (Plate 2P–Q).  Cytherella postatypica and C. pinnata are not exact mirror images. When the larger valves are compared, the Cytherella pinnata RV has a continuous bulging overlap around the entire margin; in the C. postatypica (larger) LV, the anterior margin does not.  In most locations, Cytherella pinnata adults are larger with length up to 1.18 mm versus C. postatypica which is typically 0.86–0.98 mm, though C. postatypica can be larger at Browns Creek (1.03 mm) and Castle Cove (1.07 mm).  Their occurrences and relative numbers are inconsistent, as they do not always occur together and, when they do, it is in widely varying proportions. The author has identified Cytherella pinnata from 26 of 61 outcrop samples from Browns Creek and in two of 17 samples from Castle Cove, frequently in large numbers. By contrast, Cytherella postatypica has so far been found in only seven Browns Creek and four Castle Cove samples. At these two locations the Cytherella postatypica numbers in all but one instance were very low. In Latrobe-1, by contrast, C. postatypica occurred more frequently and was nearly four times more numerous (Eglington 2006; Section 2 herein).  Though the CMS are very similar, they are not identical.

Comparison between Cytherella postatypica and C. gullrockensis McKenzie, Reyment & Reyment (1991) is hampered by the difficulties with C. gullrockensis discussed above. Illustrations of C. gullrockensis (in McKenzie et al. 1991, Plate 1, figs 2, 4) plus those of Majoran (1995, 1996b) from the Blanche Point Formation, South Australia were compared to C. postatypica as follows:  Plate 1, fig. 2 (in McKenzie et al. 1991) labelled FRV, which Neil (2006) asserts is MRV, is more elongate and less arched dorsally than either male or female Cytherella postatypica.  Majoran (1996b) FLV and Majoran (1995) FLV in lateral view are dissimilar in outline. The Majoran (1995) specimen is small, probably an A-1 female, therefore should not be compared to adults. It is more regularly ovate than juvenile forms of Cytherella postatypica. The Majoran (1996b) FLV postero-dorsal margin descends much more steeply towards the posterior end than is seen in the C. postatypica adult female.  Plate 1, fig. 4 FRV (in McKenzie et al. 1991) has a similar shape in lateral view to Cytherella postatypica and clearly demonstrates the LV>RV overlap – not mentioned by them. This is one reason why examination and comparison of the types and provision of a more detailed diagnosis and description is essential before considering conspecificity.

Castle Cove and Browns Creek are two locations studied in detail by McKenzie et al. (1993). They found Cytherella pinnata at both places but not C. gullrockensis. This author has found Cytherella pinnata and C. postatypica at both Castle Cove and Browns Creek. If Cytherella postatypica and C. gullrockensis are the same species, then McKenzie et al. (1993) would have identified it at these locations as their description of C. pinnata makes particular reference to the CMS being markedly different to C. gullrockensis, thus allowing easy recognition and differentiation between the two species. It is noted that this author found it difficult to discern clearly Cytherella postatypica adductor scars, so they may not have been readily apparent to McKenzie et al. (1993) either. It is also possible that Cytherella

Plate 2.

A-C. Cytherella atypica Bate, 1972, Toolonga Calcilutite, Carnarvon Basin, Western Australia, Late Cretaceous.

A. Paratype Io 4370 FRV. B. Paratype Io 4371 FLV internal. C. Paratype Io 4374 MC dorsal.

D-I. Cytherella batei sp. nov.

D. Paratype FCRV, Clifton Formation, Narrawaturk-2. E. Paratype FCLV, Gellibrand Marl, Heywood-10. F. Paratype MRV, Gellibrand Marl, Heywood-10. G. Holotype, FLV, Gellibrand Marl, Narrawaturk-2, 522-526 m. H. Paratype MC dorsal, Gellibrand Marl, Heywood-10. I. Paratype FLV, Clifton Formation, Narrawaturk-2.

J. Cytherella postatypica sp. nov. paratype FCLV, Pember Mudstone Member, Heywood-10.

K. Cytherella batei sp. nov. paratype FC dorsal, Gellibrand Marl, Narrawaturk-2.

L-M. Cytherella sp. cf. C. batei, Yangery-1.

L. MLV, Narrawaturk Marl, Yangery-1. M. MRV, Narrawaturk Marl, Yangery-1.

N-O. Cytherella sp. aff. C. batei, Heywood-10.

N. MLV, Gellibrand Marl, Heywood-10. O. FRV, Gellibrand Marl, Heywood-10. P. Cytherella postatypica paratype P312755 JRV, Rivernook Member, Latrobe-1, 295.35 m. Q. Cytherella pinnata paratype P312753 JRV Turritella Bed, Latrobe-1, 264.6 m.

Scale bar = 100 µ.

postatypica, due to its similarity to C. pinnata, was mixed with the latter in their assemblages and all identified as C. pinnata. It is the author’s view that the criteria for Cytherella gullrockensis lack clarity and so, apart from the comparisons and observations already made, declines to ascribe any taxa to C. gullrockensis.

In illustrations of Cytherella sp. FLV (in Whatley & Downing 1983 Plate 8, fig. 8), the CMS straddle the midline, unlike either C. postatypica or C. batei where all or most of the CMS area is above the midline. The contrasting light and dark areas (in Whatley & Downing 1983, Plate 8, figs 6 and 8) suggest the lateral surface is more undulating and laterally compressed than either of the other two species. Comparisons of lateral views reveal several differences: Cytherella sp. FLV (in Whatley & Downing 1983 Plate 8, fig. 6) has an evenly curved dorsum versus peaked arch of Cytherella postatypica; Cytherella sp. FLV (in Whatley & Downing 1983 Plate 8, fig. 8) has its maximum height behind the midline; in C. postatypica, the maximum height is medial; Cytherella sp. MRV (in Whatley & Downing 1983 Plate 8, fig. 7) has the anterior two thirds of dorsum sub-parallel to ventrum; C. postatypica angles downwards from its mid-dorsum maximum height towards the anterior margin.

Measurements. CF: length 0.80 mm, height 0.50 mm, breadth 0.38 mm. CF: length 0.75 mm, height 0.52 mm, breadth 0.40 mm. FRV: length 0.80 mm, height 0.50 mm. FRV: length 0.91 mm, height 0.60 mm. MRV: length 0.98 mm, height 0.58 mm. LV: length 0.83 mm, height 0.55 mm. MLV: length 0.60 mm, height 0.26 mm. MLV: length 0.75 mm, height 0.54 mm.

Material. Approximately 200 adult and instar valves, carapaces and fragments.

Type locality. Latrobe-1 bore.

Occurrences and age.  Pebble Point Formation: Late Paleocene (Neil 1997).  Pember Mudstone Member: Heywood-10: Late Paleocene.  Pember Mudstone Member: Latrobe-1 (Eglington 2006; Section 2 herein): Pebble Point Fauna: latest Late Paleocene/earliest Early Eocene.  Dilwyn Formation: Latrobe-1: Early Eocene (Eglington 2006; Section 2 herein).  Browns Creek Clays: Browns Creek and Castle Cove: P15-P17 foraminiferal zones, Late Eocene (Holdgate & Gallagher 2003).  Notostraea Greensand: Browns Creek: P15–P16 foraminiferal zones, Late Eocene (Holdgate & Gallagher 2003).  Lower Glen Aire Clays: Castle Cove: Early Oligocene (Holdgate & Gallagher 2003).  Narrawaturk Formation: Yangery-1, Narrawaturk-2 bores: Globigerina angiporoides – G. labiacrassata foraminiferal zone (GEDISc; GEDISd; Taylor, 1964; Chaproniere et al. 1996), Early Oligocene.  Clifton Formation: Narrawaturk-2: Faunal Units 4 & 5 (Taylor 1964), Late Oligocene – ?Early Miocene (Taylor 1964; GEDISc; Chaproniere et al. 1996).  Gellibrand Marl: Yangery-1, Heywood-10 and Narrawaturk-2 bores: Globigerina euapertura and Globoquadrina dehiscens foraminiferal zone (GEDISa; GEDISc; GEDISd; Taylor 1964; Chaproniere et al. 1996), Late Oligocene–Early Miocene.  Port Campbell Limestone: Heywood-10: Orbulina suturalis biozone, Middle Miocene (GEDISa; Chaproniere et al. 1996).

Plate 3.

A. Cytherella sp. aff. C. postatypica sp. 1, FRV, Gellibrand Marl, Yangery-1.

B. Cytherella sp. aff. C. postatypica sp. 2, CRV, Narrawaturk Formation, Yangery-1.

C-D. Cytherella sp. aff. C. postatypica sp. 3, Browns Creek Clays, Castle Cove. C. FRV. D. MRV.

E-R. Cytherella conturba sp. nov.

E-K. Bells Headland, Addis Beach. E. Paratype, FCRV. F. Paratype, FCLV. G. Holotype, FC dorsal, sinistral overlap. H. Paratype, FC dorsal, dextral overlap. I. Paratype, FC juv. dorsal, sinistral overlap. J. Paratype, FC juv. dorsal, sinistral overlap. K. Paratype, MC juv. dorsal, sinistral overlap. L. Paratype, CFLV juv. external. M. Paratype, FLV juv. internal. N. Paratype, FRV juv. external. O. Paratype, LV juv. external. P. Paratype, MRV internal, Bells Headland Addis Beach. Q-R. Paratype, detail of fig. P margin.

S. Cytherella sp. cf. C. conturba MRV length 0.82 mm, Narrawaturk Marl, Yangery-1, ~503 m. Digital photo, optical microscope.

L-O. Location “Upper bed of marine clays west of Bells Headland (Carter 4)”.

Scale bar = 100 µ except Q-R scale bar = 20 µ.

Range. Late Paleocene–Middle Miocene.

Cytherella sp. aff. C. postatypica sp. 1 Plate 3A

Description. Smooth, elongate, sub-rectangular/ovate Cytherella, with evenly convex anterior, posterior, dorsal and ventral margins. In dorsal view the lateral surface is evenly curved. The right valve internal edge would accommodate a larger left valve.

Remarks. Although this taxon is from the Miocene, it has been included because of the possession of the LV overlap.

While displaying a regular ovate shape, Cytherella sp. 1 is more elongate and smaller than Cytherella batei sp. nov. and does not have that female’s wedge-shape in dorsal view. Compared to Cytherella postatypica sp. nov. in lateral view, its margin is far more regular and evenly curved, and it lacks the peaked arch of the mid-dorsal area of C. postatypica. The lateral surface of the Cytherella sp. 1 female in dorsal view is very evenly curved with the maximum width just posterior of the midline whereas C. postatypica has maximum width occurring at an angular position well behind the midline. LV>RV.

Measurements. FRV: length 0.83 mm, height 0.5 mm. LV juv: length 0.68 mm, height 0.46 mm. LV juv: length 0.56 mm, height 0.41 mm.

Material. One female right valve, two left valve juveniles.

Occurrence and age. Gellibrand Marl: Yangery-1 bore, ~421.54 m: Globoquadrina dehiscens foraminiferal zone (GEDISd; Taylor 1964; Chaproniere et al. 1996), very Early Miocene.

Cytherella sp. aff. C. postatypica sp. 2 Plate 3B

Description. A smooth, rotund Cytherella with a broadly rounded anterior margin, highly arched dorsal margin descending steeply from the midline to the more narrowly rounded posterior margin with maximum length medial then curving to form a broadly convex ventrum. The left valve is only slightly larger than the right.

Remarks. Given its smaller size, this single specimen is presumed to be a juvenile Cytherella postatypica-like variant. It is more rotund and highly arched than the Cytherella postatypica instars to which it was compared but, as these were from other locations (due to the lack of juveniles from Yangery-1), the differences could be a regional variation.

Measurements. C: length 0.78 mm, height 0.58 mm, breadth 0.35 mm.

Material. One adult male carapace.

Occurrence and age. Narrawaturk Formation: Yangery-1 bore, 494.39 m: Globigerina labiacrassata foraminiferal zone (GEDISd; Taylor 1964; Chaproniere et al. 1996), late Early Oligocene.

Cytherella sp. aff. C. postatypica sp. 3 Plates 3C, D, 4J

Affinity. Cytherella sp. – Whatley & Downing 1983: 385, Plate, 8, figs 6–8.

Diagnosis. Smooth Cytherella with the majority of the dorsal margin parallel to the ventral margin in both male and female adult right valves, LV>RV.

Description. Smooth, moderately large Cytherella with evenly curved anterior margin, straight to weakly curved ventrum, posterior margin curving convexly then rising sharply to a point on the dorsum behind the median, the remainder of the dorsal margin is parallel to the ventral margin in both male and female adult right valves. Right valve smaller than left valve. Sexual dimorphism with females displaying twin posterior brood chambers.

Remarks. Cytherella sp. 3 is larger than Cytherella sp. Whatley & Downing (1983), but the male right valves both display parallel dorsal and ventral margins and the angled postero- dorsal section. In Cytherella batei sp. nov., the regular ovate shape does not have the steeply descending latter section of the dorsum, whereas Cytherella postatypica sp. nov. does not have the parallel anterior section of the dorsum. With only two right valves, further comparison was not possible.

Measurements. FRV: length 1.00 mm, height 0.58 mm. MRV: length 0.97 mm, height 0.60 mm.

Material. One female right valve, one male right valve.

Occurrence and age. Browns Creek Clays, 0.92 m above base of unit (sample OCC-2), Castle Cove; Late Eocene.

Cytherella sp. aff. C. postatypica sp. 4 Plate 4D-E

Description. A large, smooth, sub-ovate Cytherella, with a fragile, thin carapace wall. Anterior margin broadly, evenly rounded; dorsal margin convex; posterior is angled with respect to the median and descends to join the medially inflexed ventral margin. Dorsal view sub-ovate; maximum breadth in males behind the median. The lateral surfaces descend smoothly to the margins with no flattening out. Internally, the right valve margin stepping down to the outer edge indicates that it is the smaller valve. The CMS are behind and above the median lines; they are very visible, biserial pinnate, angled diagonally down towards the postero-ventral area and consisting of approximately 24 adductor scars.

Remarks. Unlike Cytherella postatypica, this specimen has an inflexed ventral margin and does not have the flattened area around the perimeter that is characteristic of C. batei.

Measurements. MRV: length 1.10 mm, height 0.70 mm.

Material. One MRV.

Occurrence and age. Browns Creek Clays: Browns Creek: P16–P17 foraminiferal zones, Late Eocene (Holdgate & Gallagher 2003).

Cytherella batei sp. nov. Plates 2D–I, K, 4K–P

Derivation. Named after R. H. Bate who first described the unconventional Cytherella atypica Bate (1972) in Upper Cretaceous Carnarvon Basin assemblages.

Holotype. Plates 2G, 4L, N, female left valve, Narrawaturk-2 bore, 522–526 m, Gellibrand Marl, (specimen registration number to be allocated by Museum Victoria).

Paratypes. Plates 2DF, H–I, 4K, M, O–P.

Diagnosis. A smooth, moderately large Cytherella with a regular ovate outline in lateral view, left valve overlaps right. Female carapace in dorsal view is wedge-shaped with maximum breadth well posterior of the midline. The pinnate CMS is composed of approximately 21 scars.

Description. Carapace smooth, outline ovate/sub-rectangular with anterior symmetrically curved; dorsum convex, evenly and broadly curving down to midpoint of posterior. The margin then angles from the postero-median to the straight or slightly convex ventrum. The margin possesses a narrow, less steep or flattened rim around the entire perimeter, though dorsally it is very narrow in females. Maximum length medial. Maximum height median to anterior of median. In dorsal view the carapace displays the narrow, flattened marginal zone causing the margin to protrude anteriorly and posteriorly. The larger left valve overlaps the right but in dorsal view the anterior margin of the left valve does not bulge over the right; the right margin is retracted so there is a gap allowing the inner edge of the right valve to be seen. Sexual dimorphism is evident. Males are more elongate, females are broader posteriorly having two brood chambers. Dorsal view of mature females has the carapace broadest post median in the last third to quarter of the length, resulting in a wedge shape; the profile rises steeply from the flattened anterior rim, levels off somewhat, then curves steeply down then outwards to form the protruding posterior rim. In males and juveniles, the maximum breadth is farther forward; in dorsal view it has a more ovate/tear-drop shape.

Internally, the left valve margin possesses the accommodating groove for the smaller right valve which has a raised inner edge then steps down to the outer edge. The CMS is biserial with the central axis curving forward convexly from the apex; it angles towards the posterior as it descends ventrally. The two rows appear to each consist of 10 or 11 predominantly rectangular scars. The long axes of the uppermost three scars in the anterior series are inclined towards the postero-ventral area; the long axes of the succeeding scars then increasingly angle upwards toward the postero-dorsal area. The posterior series are more regular, sloping from postero-ventral to parallel. The lowermost couple of scars of each series were not so readily visible. In total 20–22 scars.

Remarks. Though Cytherella batei resembles C. atypica Bate (1972), it is slightly larger and is notably dissimilar in dorsal view. Cytherella atypica females do not display the wedge shape of C. batei. Cytherella atypica lacks the narrow flat marginal rim of C. batei so therefore does not protrude anteriorly or posteriorly. In Cytherella atypica, the left valve overlaps the right around the entire margin; in C. batei the left valve does not curve over the right but extends anteriorly forward of the right, thus exposing the anterior inner edges of both the valves.

When Cytherella batei and C. postatypica sp. nov. are compared, the latter has maximum height arching at or near the median, often occurring as an angularity; the former does not. In

Plate 4.

A-C. Cytherella pinnata McKenzie Reyment & Reyment, 1993, RV, CMS, Browns Creek Clays, Browns Ck.

D-E. Cytherella sp. aff. C. atypica sp. 4. RV damaged postero-dorsal margin & CMS, Browns Creek Clays, Browns Creek.

F-I. Cytherella postatypica sp. nov. F. Paratype CMS, Browns Creek Clays, Browns Creek. G-I. Paratype RV juv, CMS, Browns Creek Clays, Browns Creek.

J. Cytherella sp. aff. C. postatypica sp. 3, FRV dorsal, Castle Cove.

K-P. Cytherella batei sp. nov. K. Paratype MCLV, Gellibrand Marl, Heywood-10. L. Holotype, FLV, Gellibrand Marl, Narrawaturk-2, 466-467 m. M. Paratype FC dorsal, Narrawaturk-2. N. Holotype CMS. O. Paratype FLV dorsal, Narrawaturk-2. P. Paratype FLV dorsal, Narrawaturk-2.

Q-U. Cytherella conturba sp. nov. Q. Paratype AMRV. R. Holotype FCLV. S. Holotype FC dorsal. T. Paratype FC dorsal. U. AMRV dorsal.

CMS taken with digital camera on light microscope and digitally processed (Section 10 herein). Line drawings from digital photographs.

Cytherella postatypica the flattened marginal strip described for C. batei varies from minimal to absent, particularly so along the anterior margin of the left valve. Adult females do not display the wedge-shaped dorsal view of Cytherella batei. The CMS for Cytherella postatypica and C. batei are of similar size, position and pinnate form, but C. postatypica has more scars, at least 13 in the anterior series. For Cytherella batei the top three scars in both vertical rows are in alignment with their paired partner and long axes (through the pairs) point upwards towards the antero-dorsal area, whereas in C. postatypica the anterior scars are not on the same alignment as their corresponding posterior partners―all angle downwards towards the antero-ventral area.

Cytherella sp. Whatley & Downing (1983) females are similar in lateral outline to C. batei but the male RV is much less ovate than C. batei males. Most noticeably, the straight dorsal margin is parallel to the ventrum in its anterior half then descends steeply from the dorso- median to the postero-median. Because of lack of dorsal views of females of Cytherella sp. Whatley & Downing (1983), critical comparison cannot be made.

Both Cytherella pinnata McKenzie et al. (1993) and C. aff. bellsi McKenzie et al. (1993) have RV>LV (so presumably does C. bellsi McKenzie et al. 1991) so therefore are excluded.

When the lateral views of Cytherella batei and C. gullrockensis are compared, the former lacks the angled mid-dorsal peak, is more regularly ovate in both adult males and females, and possesses a flattened marginal area that appears to be absent in C. gullrockensis. Based on the similarity between the CMS of Cytherella pinnata, C. postatypica and C. batei, and the reported dissimilarity of C. pinnata and C. gullrockensis by McKenzie et al. (1993), plus the dissimilarity in shape, conspecificity for C. batei and C. gullrockensis is rejected.

Although oval in lateral view and sinistral, Cytherella bissoni Milhau (1993) and C. chapmani Milhau (1993) from the New Zealand Early Miocene are both considerably smaller, not wedge-shaped in dorsal view, and lack the marginal extension or rim of C. batei.

Measurements. FC: length 0.92 mm, height 0.6 mm, breadth 0.4 mm. FC: length 0.87 mm, height 0.58 mm, breadth 0.33 mm. MC: length 0.89 mm, height 0.54 mm, breadth 0.32 mm. MRV: length 0.85 mm, height 0.5 mm. FLV: length 0.85 mm, height 0.52 mm. FLV: length 0.93 mm, height 0.6 mm.

Material. Thirty one male, female and juvenile valves and carapaces.

Type locality. Gellibrand Marl, Narrawaturk-2, 522–526 m.

Occurrences and age.  Narrawaturk Formation: Yangery-1, Narrawaturk-2 bores: Early Oligocene; Narrawaturk- 2 bore Globigerina labiacrassata foraminiferal zone (GEDISd; Taylor 1964; Chaproniere et al. 1996), late Early Oligocene.  Fishing Point Marl: Castle Cove: Late Oligocene.  Gellibrand Marl: Yangery-1, Heywood-10 and Narrawaturk-2 bores: Globigerina euapertura foraminiferal zone (GEDISa; GEDISc; GEDISd; Taylor 1964; Chaproniere et al. 1996), Late Oligocene.  Slide from the McKenzie Collection, Australian Museum labelled “Basal Longfordian near Princetown E of bridge on Gt. Ocean Rd. 10 Nov 64 residue via D. Taylor”: Early Miocene.

Cytherella sp. cf. C. batei Plate 2L-M

Description. A smooth, moderately large Cytherella, regular ovate shape in lateral view, left valve larger and overlapping the right.

Remarks. While displaying a regular ovate shape and similar size range to that of Cytherella batei, Cytherella sp. cf. C. batei is more elongate and less robust than C. batei sp. nov. from Narrawaturk-2. Lacking adult females, the identification is tentative.

Measurements. MRV: length 0.90 mm, height 0.52 mm. MLV: length 0.92 mm, height 0.57 mm.

Material. Two adult male valves, 13 fragments.

Occurrence and age. Narrawaturk Formation: Yangery-1 bore, ~504.5 m: Globigerina angiporoides foraminiferal zone (GEDISd; Taylor 1964; Chaproniere et al. 1996), Early Oligocene.

Cytherella sp. aff. C. batei Plate 2N, O

Description. A smooth, moderately large Cytherella, ovate in lateral view with a narrow, flattened area inside the entire margin, left valve larger and overlapping the right.

Remarks. This taxon is less regularly ovate than Cytherella batei; this is most noticeable in the female with the maximum height behind the median and the margin descending more steeply towards the antero-dorsal area. The female valve in dorsal view is similar to Cytherella batei and has the same flattened rim around the entire margin.

Measurements. Length 0.86–0.9 mm, height 0.50–0.52 mm.

Material. Two adult male valves, one adult female right valve, three juveniles.

Occurrence and age. Gellibrand Marl: Heywood-10 bore, depth 335.28 m: Globigerina euapertura foraminiferal zone (GEDIS), Late Oligocene (Chaproniere et al. 1996).

Cytherella conturba sp. nov. Plates 3E–S, 4Q–S

Derivation. From the Latin conturbo = to throw into disorder or confusion.

Holotype. Plates 3G, 4R–S, adult female carapace, Australian Museum number F139027.

Paratypes. Plates 3E–F, H–S, 4Q, three adult female carapaces, one adult male right valve, three juvenile carapaces and three valves, Australian Museum prefix F (additional registration numbers to allocated by Australian Museum).

Diagnosis. A large, smooth, reniform cytherellid. In dorsal view, adult females display a sub- rectangular shape with the lateral surfaces inclined slightly inwards towards the anterior. Both forms of valve overlap are exhibited, with carapaces having either the left valve overlapping the right valve, or the right valve overlapping the left.

Description. A large, smooth, reinform cytherellid. In lateral view, the anterior is rounded; dorsum broadly curved descending to the convex posterior margin, then descending to the rounded postero-ventral area. The ventrum is straight to concave in the smaller valve and concave in the overlapping valve. Maximum height medial, maximum length in females is near the midline, in males slightly above. In dorsal view, the female carapace is moderately compressed laterally resulting in a sub-rectangular outline with the lateral surfaces inclined slightly inwards anteriorly and broadest behind the midline. The male dorsal view is smoothly elongate sub-ovate/tear-drop shaped. The valve overlaps can be either LV dominant or RV dominant. The larger valve overlaps the smaller around the dorsal, posterior and ventral edges but the anterior margins do not overlap though the larger may protrude past the smaller but not enclose or cover its edge―thus the inner area of the marginal zone is exposed. The larger overlapping valve is slightly protuberant dorsally. There is a flattening to very slight depression in the CMS area. The CMS are bi-serial pinnate, obliquely angled from antero- dorsal to postero-ventral. In adults they are positioned above the median and at mid-length; in juveniles they are above the midline and posterior of mid-length. The CMS details could not be clearly discerned. Sexual dimorphism is present with females inflated posteriorly due to their twin brood chambers and displaying a sub-rectangular shape in dorsal view compared to the more elongate sub-ovate tear-drop shape of the single male valve. Precocious sexual dimorphism in A-1 instars with females in dorsal view wedge-shaped; males more ovate.

Remarks. While examining cytherellids in the McKenzie ostracod collection, the author observed these remarkable specimens in two slides, one an unsorted assemblage and the other a grid slide with no list of the separated specimens. Apart from the slide labels no further sampling information was available.

The sinistral Cytherella conturba adult is the same shape and within the same size-range and assemblage as the other three adult carapaces. It is so similar that, if it were not for the reversed overlap, it would unhesitatingly be considered to belong to the same species. There is precedence for valve size reversal within ostracod species in Loxoconchissa foveolata Triebel & Malz (1969) and L. spongiosa Triebel & Malz (1969) from the Romanian Lower Pliocene (Triebel & Malz 1969). The early assemblages of the two Loxoconchissa species were a mixture of “normal” and reverse carapaces, but in later assemblages this changed to “normal” (L>R) valves only (Triebel & Malz 1969). The authors remarked that the opposing valve overlaps are used to establish different species or even genera, and, as in the case of Camptocythere Triebel (1950), resulted in the questionable establishment of a new tribe, but they regarded the Loxoconchissa valve reversals as being intraspecific and of no substantial taxonomic value (Triebel & Malz 1969). It is noted that theirs were podocopids and not, as in this instance, platycopids, for which there would seem to be no such precedence. Cytherella conturba is within the lower end of the size-range for C. bellsi McKenzie et al. (1991), but the latter is described as having a convex ventrum in females, weakly inflexed medially in juveniles and adults and possessing a postero-marginal transverse ridge. Cytherella conturba female RVs are weakly concave, the juvenile ventrum is convex, and it lacks the postero- marginal ridge.

Cytherella pinnata McKenzie et al. (1993) does not possess the reniform outline of C. conturba nor has it the female sub-rectangular shape in dorsal view. Similarly, female dorsal views of Cytherella postatypica sp. nov. and C. batei sp. nov. are dissimilar to C. conturba, the first being wedge-shaped and the second ovate.

Cytherella conturba has a similar size range to the Late Eocene South Australian C. gullrockensis McKenzie et al. (1991) but the lack of detail in their diagnosis and description, in particular, its dorsal view, valve overlaps and shape of juveniles, plus the inability to locate

93 types and the absence of identified specimens in the McKenzie collection, render comparisons between large, smooth, ovate cytherellids and C. gullrockensis problematic. Both dextral and sinistral forms may have been present in the original McKenzie et al. assemblages, either as intraspecific or interspecific variation, but were overlooked and, by happenstance, the specimen chosen for illustration (in McKenzie et al. 1991, Plate 1, fig. 4) showed the LV overlap. In lateral view Cytherella conturba is reniform compared to either C. gullrockensis McKenzie et al. (1991) or Cytherella sp. cf. C. gullrockensis Neil (2006). Cytherella gullrockensis Majoran (1995), with a length of 0.84 mm, is most probably a juvenile; his figured FLV specimen (Majoran 1996) is markedly steeper in lateral view where the dorsum descends to the posterior area.

Measurements. Adults, RV>LV: FC paratype: length 0.95 mm, height 0.55 mm, breadth 0.42 mm. FC paratype: length 0.95 mm, height 0.54 mm, breadth 0.41 mm. FC paratype: length 0.91 mm, height 0.53 mm, breadth 0.40 mm. Adult, LV>RV: FC holotype: length 0.93 mm, height 0.57 mm, breadth 0.47 mm. MRV paratype: length 1.0 mm, height 0.53 mm. Juveniles, RV>LV FC paratype: length 0.63 mm, height 0.43 mm, breadth 0.33 mm. FC paratype: length 0.58 mm, height 0.40 mm, breadth 0.31 mm. FC paratype: length 0.56 mm, height 0.39 mm, breadth 0.31 mm. Juvenile, LV>RV MC paratype: length 0.55 mm, height 0.37 mm, breadth 0.25 mm. LV paratype: length 0.51 mm, height 0.34 mm.

Material. Four adult carapaces (3 dextral, 1 sinistral) and four juvenile carapaces (3 dextral, 1 sinistral) from grid slide square #39, and two valves (1 LV juv., 1AMRV) from slide labelled Bells Headland Addis Beach upper level.

Locality. Grid slide, square #39, labelled “Upper bed of marine clays west of Bells Headland (Carter 4)” from tray 7, McKenzie Cabinet 2, McKenzie Collection, Marine Invertebrate Biology, Australian Museum, College Street, Sydney. The valves were from an unsorted well- slide assemblage labelled “Bells Headland Addis Beach upper level” (cabinet 2, tray 7).

Occurrence and age. Based on the grid slide label referring to “clays west of Bells Headland”, it is concluded that the marine clay sample is Jan Juc Formation of Late Oligocene age (P21-P22, Holdgate & Gallagher 2003). The same stratigraphic assumption and age is made for the slide “Bells Headland Addis Beach upper level”. It is most probable that which “Carter 4” refers to “Faunal Unit 4 from the basal part of the Jan Juc Formation on the west side of the Bells Headland in the Torquay district” (Carter 1964). Faunal Unit 4, Victoriella conoides is Oligocene (Chaproniere et al. 1996).

Cytherella sp. cf. C. conturba Plate 3S

Description. A smooth, elongate, reniform Cytherella with a low, arched dorsum, evenly curved anterior and posterior margins and concave ventrum. The right valve margin displays the appropriate profile for accommodating a larger left valve.

Remarks. This single damaged valve is much more elongate than either Cytherella batei, C. postatypica or their affiliates; its shape in lateral view is closer to that of the AMRV C. conturba sp. nov. but smaller.

Measurements. MRV: length 0.82 mm, height 0.48 mm.

Material. One adult male right valve.

Occurrence and age. Narrawaturk Formation: Yangery-1 bore, ~503 m: Globigerina angiporoides foraminiferal zone (GEDISd; Taylor 1964; Chaproniere et al. 1996), Early Oligocene.

DISCUSSION

The earliest appearance of a Cytherella with left valve overlapping right is in the Late Cretaceous of Western Australian (Bate 1972; Damotte 1992). The species, or a closely related one, migrated south and eastward into the developing Australo-Antarctic Gulf to appear as Cytherella postatypica sp. nov. in the Late Paleocene Pebble Point Formation and the Pember Mudstone, southern Victoria (Neil 1997; Eglington 2006; Sections 2 and 9 herein). Cytherella postatypica, found in the Otway Basin area through to the Middle Miocene (Fig. 3), is the most widely distributed and longest ranging of the sinistral species, and is one that tolerated low oxygen substrates (Sections 3 & 5 herein).

Conspecificity was considered for Cytherella postatypica and C. pinnata McKenzie et al. 1993, a local species but with right-over-left valve overlap. The two are very similar in shape, size and CMS, and frequently occur together from the Late Paleocene to Middle Miocene. Differences between the two are small but consistent, and were regarded as sufficient for their recognition as separate species. Cytherella pinnata specimens are almost always larger, the postero-dorsal margin descending to the posterior more steeply; the larger valve has a thicker, more continuous marginal bulge overlapping the smaller valve. In lateral view the juveniles have a more triangular shape caused by the angular posterior. Though very similar, the CMS are not identical; the ventral margin of adult males may be inflexed but is never so in C. postatypica. The two species often occur together, but this is not consistent, nor are their relative proportions in any assemblage.

As variants of Cytherella postatypica evolved, the more symmetrical sinistrals first appeared in the Early Oligocene (Cytherella sp. cf. C. batei and C. sp. aff. C. batei ); by Late Oligocene C. batei sp. nov. inhabited marine environments at Castle Cove, Heywood-10, Narrawaturk-2 and Yangery-1, and in the Early Miocene at Princetown (Fig. 3).

A species of Cytherella with either left or right valve dominant, C. conturba sp. nov., emerged in the Late Oligocene in the Bells Headland area. The discovery of this taxon and the close relationship that appears to exist between Cytherella postatypica and C. pinnata challenge the genus Inversacytherella Swanson et al. (2005), erected primarily to accommodate sinistral Cytherella. As other characters regarded as diagnostic for Inversacytherella are inconsequential―now including valve overlap (inferred to be intraspecific)―that nominal genus is placed in the synonymy of Cytherella s.s.

Opening of the Tasmanian Gateway enabled sinistral taxa to migrate across the Tasman to New Zealand where they evolved to become Cytherella bissoni Milhau (1993) and C. chapmani Milhau (1993) (Early Miocene). The sinistral modification is extant in the Recent species Cytherella splendida Swanson (1993) inhabiting the East Tasman Sea.

If sinistral taxa simply evolved in the Late Cretaceous of Western Australian, migrated into the Australo-Antarctic Gulf and Tasman Sea, and evolved into further sinistral forms, it is difficult, without better understanding of the interplay of genotypic and phenotypic

95 influences, to explain the possibility of a close relationship between Cytherella atypica and C. pinnata, and the subsequent appearance of the bi-symmetrical C. conturba. There is scope for further consideration of the phenomenon of valve overlap in these Cytherella especially to determine if there might be soft-part morphology that differentiates sinistrals from dexters.

M. Miocene H-10 E. Miocene Princetown N. Z.: C. bissoni C. chapmani v. E. Miocene C. sp. 1: Y-1 L. Oligocene/ H-10, N-2, Y-1 E. Miocene L. Oligocene/ N-2 ?E. Miocene L. Oligocene Castle Cove H-10, N-2, Y-1 C. conturba: Bells Headland C. batei l. E. Oligocene C. aff. conturba: Y1 C. sp. 2: Y-1 E. Oligocene Castle Cove, N-2, Y-1 C. cf. batei: Y-1 C. aff. batei: Y-1 L. Eocene Browns Ck C. aff. postatypica C. sp. 3 Browns Creek Castle Cove E. Eocene L-1

L. Paleocene C. postatypica Pebble Point Late Cretaceous C. atypica & C. aff. atypica Western Australia

Fig. 3. Range and distribution of sinistral Cytherella (H-10 = Heywood-10; L-1 = Latrobe-1; N-2 = Narrawaturk-2; Y-1 = Yangery-1 bores; N. Z. = New Zealand).

CONCLUSION

Sinistral Cytherella are endemic to the Australia-New Zealand region. They originated in the Late Cretaceous of Western Australian, migrated into and colonised the shallower shelf habitats of the Australo-Antarctic Gulf from the Late Paleocene then via the Tasmanian Gateway into Tasman Sea Late Paleogene locations (DSDP 207 & 277) on the Lord Howe Rise and Campbell Plateau (Millson 1987; Ayress 1994, Ayress lit. comm. 2014) . One sinistral taxon of Cytherella occurring in the present-day eastern Tasman Sea provides an opportunity for elucidating if differences are also present in the anatomy of their soft-parts, and to test whether the nature of the valve overlap is affected by variations in environmental conditions.

The study has clarified some of the taxonomy, evolutionary history and relationships of sinistral Cytherella. Still needed are dorsal-view illustrations of some forms, re-sampling of type localities in quest of material for possible selection of neotypes where type specimens appear to have been lost, and obtaining more information on Cytherella conturba and of the taxa currently in open nomenclature where numbers of specimens have been low or insufficient. The last of these desiderata may provide more precise stratigraphic ranges for some of the taxa and more precision regarding their dispersal and habitats.

ACKNOWLEDGEMENTS

Grateful thanks for extensive supervisory guidance, support and editorial comment are extended to Kelsie Dadd, John A. Talent and Ruth Mawson of Earth and Planetary Sciences,

Macquarie University. The comments and recommendations of the referees Michael Ayress, Alan Lord and Mark Warne are deeply appreciated and grateful thanks extended.

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MCKENZIE, K. G. & GUHA, D. K., 1987. A comparative analysis of Eocene/Oligocene boundary Ostracoda from southeastern Australia and India with respect to their usefulness as indicators of petroleum potential. Transactions of the Royal Society of South Australia 111(1), 15-23. MCKENZIE, K. G. & NEIL, J. V., 1983. Promanawa gen. nov., an Australian Miocene punciid ostracode from Hamilton, Victoria. Proceedings of the Royal Society of Victoria 95, 59-64. MCKENZIE, K. G. & PEYPOUQUET, J.-P. 1984. Oceanic palaeoenvironment of the Miocene Fyansford Formation from Fossil Beach, near Mornington, Victoria, interpreted on the basis of Ostracoda. Alcheringa 8, 291-303. MCKENZIE, K. G., REYMENT, R. A. & REYMENT, E. R., 1990. Pleistocene and Recent Ostracoda from Goose Lagoon Drain, Victoria and Kingston, South Australia. Bulletin of the Geological Institutions of the University of Uppsala, Uppsala, N. 16, 1- 46. MCKENZIE, K. G., REYMENT, R. A. & REYMENT, E. R., 1991. Eocene-Oligocene Ostracoda from South Australia and Victoria, Australia. Revista Española de Paleontologia 6(2), 135-175. MCKENZIE, K. G., REYMENT, R. A. & REYMENT, E. R., 1993. Eocene Ostracoda from the Browns Creek Clays at Browns Creek and Castle Cove, Victoria, Australia. Revista Española de Paleontologia 8(1), 75-116. MILHAU, B., 1993. Nouveaux Ostracodes du Miocène inférieur de Nouvelle-Zélande. Geobios 26, 2, 161-200. NEIL, J. V., 1994. Miocene Ostracoda of the Trachyleberididae and Hemicytheridae from the Muddy Creek area, south-western Victoria. Memoirs of the Museum of Victoria 54, 1-49. NEIL, J. V., 1995. Palaeobiogeography of some Oligocene-Miocene ostracode assemblages from southeastern Australia. In Ostracoda and Biostratigraphy - Proceedings of the 12th. International Symposium on Ostracoda, Prague, 1994. A. A. Balkema, Rotterdam, 215-224. NEIL, J. V., 1997. A Late Paleocene ostracode fauna from the Pebble Point Formation, south-west Victoria. Proceedings of the Royal Society of Victoria 109, 167-197. NEIL, J. V., 2000. Factors influencing intraspecific variation and polymorphism in marine podocopid Ostracoda, with particular reference to Tertiary species from southeastern Australia. Hydrobiologia 419, 161-180. NEIL, J. V., 2002. Variation in surface morphology of a Miocene hemicytherid ostracode. Alcheringa 26, 289-297. NEIL, J. V., 2006. Taxonomy of an ostracode assemblage from the Middle Miocene Wuk Wuk Marl, Gippsland, Victoria. Proceedings of the Royal Society of Victoria 118(1), 35-63. SARS, G. O., 1866. Oversigt af Norges marine ostracoder. Förhandl, Vidensk, Selskab Christiania 7, 1-130. SWANSON, K. M., JELLINEK, T. J. & MALZ, H. 2005. The platycopine condition, new observations on reproduction, respiration and feeding in living deep-sea Platycopina (Crustacea, Ostracoda). Senckenbergiana maritima 35(2), 157-187. TAYLOR, D. J., 1964a. Biostratigraphic log Latrobe No. 1 bore. Geological Survey of Victoria, Unpublished Report, PE990957, Department of Manufacturing and Industry Development, Melbourne, 1-3.

TAYLOR, D. J., 1964b. Biostratigraphic log Narrawaturk No. 2 bore. Geological Survey of Victoria, Unpublished Report, Department of Manufacturing and Industry Development, Melbourne, 1. TAYLOR, D. J., 1965. Preservation, composition, and significance of Victorian Lower Tertiary ‘Cyclammina faunas’. Proceedings of the Royal Society of Victoria NS 78 (2), 143-160. TAYLOR, D. J., 1966. Esso Gippsland Shelf No. 1 the Mid-Tertiary foraminiferal sequence. Bureau of Mineral Resources, Geology and Geophysics, Australia Publication of Petroleum Search Subs Acts Australia 76, 31-46. TAYLOR, D. J., 1971. Chapter 10 – Foraminifera and the Cretaceous and Tertiary depositional history. In The Otway Basin of Southeastern Australia, H. Wopfner & J. G. Douglas, eds, Special Bulletin, Geological Surveys of South Australia and Victoria, 217-234, enclosures 10.1-10.2. TRIEBEL, E., & MALZ, H., 1969. ‘Normale’ und inverse Gehäuse bei den Loxoconchinae (Ostracoda), Loxoconchissa n. gen. Senckenbergiana lethaea 50 5/6, Frankfurt am Main, 20, 12, 447-463. VAN MORKHOVEN, F.P.C.M., 1963. Post-Palaeozoic Ostracoda, Their Morphology, Taxonomy and Economic Use. Vol. 2. Elsevier, Amsterdam, London, New York, 478 pp. WARNE, M. T., 1986. Paranesidea and Papillatabairdia (Ostracoda, Crustacea) from the Miocene of the Port Phillip and Western Port Basins, Victoria, Australia. Proceedings of the Royal Society of Victoria 98, 41-48. WARNE, M. T., 1987. Lithostratigraphical associations of the ostracode fauna in the marine Neogene of the Port Phillip and Western Port Basins, Victoria. In Shallow Tethys 2, The Proceedings of the International Symposium on Shallow Tethys 2, Wagga Wagga, 15-17 September 1986, K. G. McKenzie, ed., A. A. Balkema, Rotterdam, Boston, 435-445. WARNE, M. T., 1988. Neonesidea and Bairdoppilata (Ostracoda) from the Miocene of the Port Phillip and Western Port Basins, Victoria, Australia. Alcheringa 12, 7-26. WARNE, M. T., 1990a. Polycopidae (Ostracoda, Crustacea) from the Late Tertiary of the Port Phillip and Western Port Basins, Victoria. Proceedings of the Royal Society of Victoria 102(1), 59-66. WARNE, M. T., 1990b. Bythocyprididae (Ostracoda) from the Miocene of the Port Phillip and Western Port Basins, Victoria. Proceedings of the Royal Society of Victoria 102 (2), 105-115. WARNE, M. T., 1996. The evolutionary significance of scale-like spines on the Australian and SW Pacific Cainozoic ostracods Ponticocythereis manis Whatley and Titterton, 1981 and Trachyleberis floridus sp. nov. Journal of Micropalaeontology 15, 161-168. WARNE, M. T., 2002. Palaeo-geomorphological significance of Miocene and Pliocene euryhaline Ostracoda in the Nepean 1 borehole, Port Phillip Basin, SE Australia. Memoirs of the Association of Australasian Palaeontologists 27,139-148. WHATLEY, R. & DOWNING, S., 1983. Middle Miocene Ostracoda from Victoria, Australia. Revista Española de Micropaleontologia 15(3), 347-407. WOPFNER, H. & DOUGLAS, J. G., 1971. 1 Area and regional setting. In The Otway Basin of Southeastern Australia. H. Wopfner & J. G. Douglas, eds, Special Bulletin, Geological Surveys of South Australia and Victoria, Ministry of Development and Mines, South Australia and Ministry of Mines, Victoria, 17-25. YASSINI, I. & JONES, B. G., 1995. Recent Foraminifera and Ostracoda from Estuarine and Shelf Environments on the Southeastern Coast of Australia. University of Wollongong Press, Wollongong, NSW, Australia, 484 pp.

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SECTION 5

CHANGING LATE PALEOCENE AND EARLY EOCENE PALAEOENVIRONMENTS NORTHEASTERN AUSTRALO-ANTARCTIC GULF USING OSTRACODA AND FORAMINIFERA

COL EGLINGTON

Department of Earth and Planetary Sciences, Macquarie University, Sydney, NSW 2109, Australia. [email protected]

EGLINGTON, C. Changing Late Paleocene and Early Eocene palaeoenvironments northeastern Australo-Antarctic Gulf using Ostracoda and Foraminifera.

Key words. Paleocene, Eocene, Ostracoda, Foraminifera, Wangerrip, Dilwyn, Rivernook, Latrobe-1, Heywood-10, Otway Basin, Australia, Paleocene-Eocene boundary, Australo- Antarctic Gulf, dysoxia, palaeoenvironment, Rivernook Ingression.

ABSTRACT

Marine benthic ostracod (Crustacea) genera are particularly suited to palaeoenvironmental interpretations as they can tolerate only limited changes in conditions, in particular temperature and depth. The availability of 26 assemblages from four Late Paleocene and Early Eocene sites in the Otway Basin, Victoria, provides a unique opportunity to use these organisms to assess the marine conditions at these locations, in particular during the Early Eocene Rivernook Ingression. The two subsurface sections (Latrobe-1 and Heywood-10 bores) and two outcrops (Pebble Point and Rivernook) cover the Pebble Point and Dilwyn Formations of the Wangerrip Group.

The Early Eocene locations were all shallow, near-shore and within the enclosed eastern end of the Australo-Antarctic Gulf (AAG). Differences in both ostracod and foraminiferan assemblage taxa demonstrate the variability of local conditions during the Rivernook Ingression. The Pebble Point Formation marine benthos was apparently cool, well oxygenated, and deeper than the younger Rivernook Member. The Pember Mudstone environment at the Heywood-10 and Latrobe-1 bores, was one of restricted circulation possibly with a very poorly oxygenated benthos in a warm, shallow, marginal marine setting. The Rivernook Member was shallow epineritic to neritic, warm, marine with benthic oxygenation possibly ranging from very high to very low. The Dilwyn Formation above the Rivernook Member had fluctuating O2 levels through high to low in generally warm, shallow conditions. The Platycopid Signal Hypothesis was applied to the ostracod assemblages and the results compared with foraminiferan data, it was found to concur in six instances, was contradicted in two and ambiguous in three, its veracity could not be definitively decided.

INTRODUCTION

Major changes in ocean circulation, continental configuration and climate characterise the Paleocene and Eocene (Aubrey et al. 1998). Global deep-sea oxygen and carbon isotope records indicate that the mid-Paleocene to early Eocene (59–52 Ma) experienced a pronounced warming trend with a geologically brief period of more intense warming in the Paleocene–Eocene Thermal Maximum (PETM) at ~55.0 Ma (Kroon et al. 2007) and the 52– 50 Ma Early Eocene Climatic Optimum (EECO) (Berggren et al. 1998; Zachos et al. 2001).

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Sea temperatures in high latitudes were warm, with sea surface temperatures estimated at around 14–16º C and ~10–14º C in benthic environments (Berggren et al. 1998). Polar caps, ice sheets and glaciers were nonexistent (Thomas 1998; White 2004), removing the source of high latitude thermohaline-driven cold-water bottom currents. In the absence of oceanic temperature stratification within the water column, halothermal circulation took over (Kennett & Stott 1990). Bottom waters generally were warm, saline, O2 poor and corrosive, resulting in widespread CaCO3 dissolution (Steineck & Thomas 1996; Berggren et al. 1998; Thomas 1998). Radical oceanic and climatic changes were responsible for significant turnover in marine (Steineck & Thomas 1996; Berggren et al. 1998; Kroon et al. 2007) and terrestrial biota (Gunnell 1998; Wing 1998; Luterbacher et al. 2004). The extreme warming was associated with a large negative δ13C excursion (Beck et al. 1998; Zachos et al. 2001; Luterbacher et al. 2004), extinctions in planktonic and benthic foraminiferans, and changes in global productivity (Berggren et al. 1998; Thomas 1998; Boersma et al. 1998). In some locations other groups, including ostracods (Steineck & Thomas 1996), were also adversely affected. There was a notable reduction in global atmospheric circulation, an accompanying decrease in low latitude surface-water temperatures despite the warmer high latitudes, and changes in the physico-chemical composition and transport of water masses (Steineck & Thomas 1996; Boersma et al. 1998). These conditions gradually ameliorated resulting in a more or less steady fall in deep-sea water temperature from the Early Eocene into the Early Oligocene (Zachos et al. 1994, 2001).

The separation of Australia and Antarctica that commenced in the Late Cretaceous (Exon et. al 2004d) was well underway by the end of the Paleocene creating the Australo-Antarctic Gulf (AAG) (Duddy 2003; Cande & Stock 2004), an almost completely enclosed, deep marine basin, with extensive shallow continental shelves, open at the western end to inflowing warm surface waters from the Indian Ocean. A west–east current is assumed to have flowed along the northern region, part of a weak, clockwise gyre (Exon et al. 2004d). Extrapolation from ODP data collected at the eastern end of the AAG indicate that in the Late Paleocene–Early Eocene this area was a highly restricted, moderately tranquil, broad shelf with little current or tidal influence, poorly ventilated, dysoxic and with an expanded Oxygen Minimum Zone (OMZ) extending up the continental shelf (Exon et al. 2001; Exon et al. 2004d).

The locations for this study are all within the Otway Basin, southern Victoria (Fig. 1). In the Early Eocene this basin was towards the northeastern end of the AAG. The locations were on the shallow, continental shelf at about 60°S latitude (Cande & Stock 2004; Exon et al. 2004d). Due to the shelf position of the Princetown area (Fig. 1) within the enclosed eastern end of the AAG, the water would have been considerably warmer than oceanic temperatures (Exon et al. 2004d).

The availability of 26 ostracod assemblages from four Late Paleocene and Early Eocene sites (Eglington 2006; Sections 2 & 3 herein) plus extensive foraminiferal data provided a unique opportunity to use the ostracod assemblages to assess marine conditions at the locations. A method for estimating benthic dissolved O2 based on the percentage of platycopid ostracods in an assemblage was applied, and its veracity assessed by comparison with the foraminiferans.

GEOLOGICAL SETTING

The Otway Basin is one of a series of basins in southern Australia formed during Gondwana rifting (Krassay et al. 2004). The basin is east-west trending, approximately 500 km in length, extends both on and off shore, and contains thick Mesozoic and Cenozoic strata. The basal Cenozoic unit in the eastern onshore area of the basin is the Wangerrip Group, a sequence of

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Paleocene–Middle Eocene sedimentary rocks comprising the basal Paleocene Pebble Point Formation and the predominantly Eocene Dilwyn Formation. The base of the Wangerrip Group rests unconformably on Cretaceous sedimentary rocks (Wopfner & Douglas 1971; Abele et al. 1993; Holdgate & Gallagher 2003). The Wangerrip Group is predominantly paralic marine to brackish throughout with periods of increased circulation (McGowran 1965), and is interpreted by Arditto (1995) as inner estuarine channel sandstone. The main structural components of the Victorian eastern onshore part of the basin (Fig. 1) are the Warrnambool and Otway Ranges Highs, and the Port Campbell and Tyrendarra Embayments (Wopfner & Douglas 1971. The Heywood-10 bore is situated within the latter (Fig. 1).

Fig. 1. Bore locations and relevant structural features, Otway Basin, Victoria (after Wopfner & Douglas 1971).

The Pebble Point Formation consists of sandstones, gritstones, claystones and conglomerates. It is found in a coastal outcrop (Fig. 2), and subsurface in the Yangery-1, Narrawaturk-2, Heywood-10 and Latrobe-1 bores (Fig. 1) (Glenie 1971; Abele et al. 1976; Holdgate & Gallagher 2003). The depositional environment was mainly transgressive shallow marine (Holdgate & Gallagher 2003).

The overlying Dilwyn Formation has been interpreted as paralic, deposited in a fairly shallow, neritic, shelf to estuarine environment, in water fluctuating from marine to brackish with deltaic, lagoonal and tidal flat sequences (Taylor 1965; Bock & Glenie 1965). The lowermost member of the Dilwyn Formation is the Pember Mudstone, a prodelta sequence of marine shale grading upwards into delta-front facies, the unit’s sandstone includes beach and offshore bar deposits (Holdgate 1981). The Rivernook and Princetown Members, and the Rivernook A, Trochocyathus and Turritella beds are richer fossiliferous strata interbedded within the Dilwyn Formation.

Rivernook A is glauconitic and siliciclastic marine mudstone within the Dilwyn Formation slightly below the Rivernook Member. The outcrop is usually covered by beach sand (Taylor 1964a, 1964d, 1965, Taylor in McGowran 1970). Taylor (1970 pers. comm.) located the Rivernook A bed in the Latrobe-1 bore at 304.8–305.4 m in an interval of poor core recovery. McGowran (1989, 1991; McGowran et al. 1997, 2000, 2004) identified Rivernook A (Table 1) as representing a significant marine ingression at, or just above, the Paleocene–Eocene Boundary.

The Rivernook Member outcrops in a coastal section southeast of Point Ronald in southern Victoria. It is a 6.1 m thick, fine-grained, siliciclastic, sandy mudstone containing glauconite, abundant terrigenous plant matter and marine fossils; its base is 167.6 m above the base of the

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Fig. 2. Rivernook Member locations (Rivernook and Latrobe-1) near Princetown, Otway Basin, Victoria (Eglington 2006).

Wangerrip Formation (Baker 1950). The unit is not lithologically distinct in subsurface material, but its fauna and flora content (McGowran 1965, 1970; Taylor 1964a, 1964d, 1965; Harris 1965; Eglington 2006; Section 2 herein) enabled it to be located in Latrobe-1 bore between 292 and 304.8 m (Taylor 1964a, 1965; Eglington 2006) and in Heywood-10 bore at 1217 m (Taylor 1964d, 1965, 1971). Based on the foraminiferans, McGowran (1989, 1991; McGowran et al. 1997, 2000, 2004) identified the Rivernook Member as an important marine ingression at, or just above, the Paleocene–Eocene Boundary.

The position of the Rivernook Member in the Princetown area relative to shore-line is conjectural as the timing of the emergence of the nearby Otway Ranges is problematic, with dates ranging from Lower Cretaceous to Neogene (Bryan & Reynolds 1971; Krassay et al. 2004). Evidence however suggests the uplift largely post dated the Early Eocene (Edwards 1962; Douglas 1977; Krassay et al. 2004). If the rise above sea level was post Early Eocene, then the Early Eocene coast may have been much farther to the north (based on Enclosure 9.3 in Wopfner and Douglas 1971) and an estuarine system could have been very extensive. If significant uplift was earlier, then the shoreline could have been very close to the Princetown area. The presence of planktonic foraminiferans in the Rivernook sedimentary rocks (Taylor 1970 pers. comm.) requires either scenario to have periods of open marine conditions. The haphazard patterns of foraminiferal assemblages found in the Latrobe-1 bore (Fig. 1) suggest physico-chemical fluctuations in the environment that were most likely to have been caused by circulation changes (Taylor 1971).

The Trochocyathus and Turritella beds occur between the Princetown and Rivernook Members in the Dilwyn Formation in outcrop at Princetown and in the Latrobe-1 bore (Baker 1950; Taylor 1964a, 1970). In Latrobe-1, Eglington (2006) placed the Trochocyathus Bed at 257.86 m and the Turritella Bed at 262–264.5 m.

The Princetown Member is restricted in occurrence and was initially described as unfossiliferous by Baker (1950) from outcrop at Princetown. Subsequently both he and Taylor

104 extracted the foraminiferan Cyclammina, incorrectly identified by Taylor as Haplophragmoides (Baker 1953; Taylor 1970 pers. comm.; Ludbrook 1977). The unit was located subsurface in Latrobe-1 bore at 228.6 m (Taylor 1964a, 1965).

A series of Late Paleocene and Early Eocene regional marine transgressions/ingressions have been identified, correlated and dated from their foraminiferal content, and named after the strata in which they occur (Table 1), they are the Pebble Point, Rivernook-A, Rivernook and Princetown ingressions (McGowran et. al 2000, 2004).

Planktonic Taylor Pollen Ingressions Stages Zones Zones Zones

M. diversus

Eocene

Princetown Early P7 Q, R Rivernook P6b S

Rivernook-A P6a T

Late Upper L. Pebble Point P5 U Paleocene balmei

Table 1. Pebble Point, Rivernook-A, Rivernook and Princetown ingressions, Otway Basin, Victoria (McGowran et. al 2004); M. diversus = Malvacipollis diversus; L. balmei = Lygistepollenites balmei.

The Pebble Point Formation is overlain by the Pember Mudstone/Dilwyn Formation ranging in age from Middle Paleocene–Early Eocene, spore/pollen zones L. balmei–M. diversus (Holdgate & Gallagher 2003). The Rivernook A and Rivernook marine ingressions are considered to be Chron 24, Early Eocene. Rivernook A is dated as earliest Early Eocene (Ypresian), planktic foraminiferal zone P6a and the Rivernook Ingression as Early Eocene (Ypresian), upper Chron 24, P6b zone (McGowran et al. 2000). The Princetown Member has been dated as foraminiferal zone P7 ( McGowran (1991).

FORAMINIFERAL FAUNAS

Taylor (1964a, 1965, 1970 pers. comm., 1971) and McGowran (1965) identified and described distinctive foraminiferal assemblages from the Wangerrip Group, including the “Princetown”, “Trochocyathus”, “Rivernook” and “Pebble Point” faunas. Taylor (1964a, 1965, 1970 pers. comm., 1971) examined foraminiferal assemblages from Latrobe-1 and Heywood-10 bores, and outcrop of the Princetown, Rivernook and Pebble Point Members, and the Trochocyathus and Rivernook A beds. He used the results for dating, depositional history, and construction of a facies sequence for Latrobe-1 bore (Taylor 1965, 1971) but did not publish the biostratigraphic data that underpinned his results, hence the necessity for presenting the relevant information. The terms Pebble Point, Rivernook, Trochocyathus and Princetown faunas were used by Taylor (1964a, 1964d, 1965, 1970 pers. comm., 1971) and McGowran (1965) and refer to biostratigraphic units based on their foraminiferal assemblages; these terms have been retained. When referring to sample-based groups of ostracods or foraminiferans, the term assemblage has been applied.

Referring to the units as ‘faunas’ could give the impression that each is distinctively individual, Eglington (2006) accepted the implication that there were characteristics unique to each of the faunas, but this is less evident on closer examination, and when the faunas are compared there is considerable species conformity. There is a degree of non-overlap of taxa in the Pebble Point fauna when comparing it to younger faunas (Taylor 1970 pers. comm.;

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McGowran 1965); the Rivernook fauna contains signatory taxa that differentiate it from the Pebble Point fauna but are also present in the Trochocyathus and Princetown faunas (Taylor 1970 pers. comm.). Therefore, apart from specimen numbers, differences between the Rivernook fauna and the smaller up-section assemblages are less easily demonstrated, especially at the individual sample level. In addition, the small numbers of specimens due to up-section impoverishment make comparisons difficult. The Rivernook A fauna, however, has a large variety of planktonics, probably as the result of a short period of unrestricted open marine circulation not experienced to the same degree by the other faunas.

Some of Taylor's foraminiferal numbers are very low. His categories for specimen numbers were: 1, 2–5, 5–10, 10–20, 20+. For calculations, these have been treated as: 1, 2–5, 6–10, 11–20, 21+, and the means used, and combined with Taylor’s (1971) cumulative percentages. Based on the cumulative percentages for the core samples, the 20+ category (with no upper limit) was determined to be frequently at or near the lower limit and has been treated as 21 specimens. The percentages of his foraminiferal taxa relative to their numbers were:

Single specimen taxa = 37 2-5 specimens = 39 6-10 “ = 12 11-20 “ = 6 21+ “ = 6 100%

Foraminiferal identifications are given as listed by Taylor (1970 pers. comm.), except for the replacement of the genus Haplophragmoides with Cyclammina, based on revisions by Ludbrook (1977). The Pebble Point fauna has received less attention in this study due to the very small number of ostracods.

The agglutinated foraminiferan Cyclammina is an important environmental indicator in the assemblages. Cyclammina is a shelf to estuarine benthic inhabitant that flourishes in oxygen- poor, siliciclastic-rich marginal marine environments (Ludbrook 1977; McKenzie 1979; Li et al. 2003). Ludbrook (1977) interpreted Cyclammina-bearing sedimentary rocks of the Otway Basin (such as the Rivernook strata) as having been laid down in fairly shallow shelf to estuarine conditions. Both the foraminiferal genera Haplophragmoides and Cyclammina are present in Rivernook beds and can tolerate low oxygen environments (Ludbrook 1977).

The foraminiferan faunas rank as follows in order of abundance and diversity (highest to lowest): Rivernook, Trochocyathus, Pebble Point, Princetown (Taylor 1970 pers. comm.).

Pebble Point fauna

The oldest of the foraminiferal faunal zones, the Pebble Point fauna, is distinctive and was initially described from outcrop material (Taylor 1964a, 1964d, 1964c, 1964d, 1965, 1970 pers. comm. 1971; McGowran 1965, 1970). This faunal zone was also identified in Latrobe-1 and Heywood-10 bores in both the Pebble Point Formation and continuing above into the Dilwyn Formation (Taylor 1964a, 1964d, 1964c, 1964d, 1965, 1970 pers. comm., 1971).

Rivernook fauna

The interval from ~289.6 to ~306 m in Latrobe-1 bore contains the Rivernook Member and Rivernook A Bed. The Rivernook A Bed (~300 to ~305.4 m) has only 21% core recovery so precise unit boundaries are not possible (Taylor 1964a). The Rivernook fauna is the most

106 diverse and prolific of the four faunas with 71 foraminiferal taxa, 26 of which do not occur in the Princetown/Trochocyathus faunas. The faunal compositions range from 0–80% planktonics, ~7 to ~55% nodosariids, 0 to ~20% cibicidids, 0 to ~14% buliminids and 10 to ~85% agglutinated; the dominant taxa are Cyclammina rotundata, Praeglobobulimina quadrata and Anomalinoides aff. noblis (Taylor, 1965, 1970 pers. comm., 1971).

The planktonic “flood” (~80% planktonics) in Rivernook A at 304.8 m (Taylor 1971) is spread across 12 taxa making it the most diverse planktonic assemblage in the section; 11 of these 12 taxa also occur in Rivernook A outcrop. Deposition of the Rivernook A Bed and base of the Rivernook Member appear to correspond with a sudden and dramatic, though brief, inflow of open marine surface water, which is then greatly reduced as the planktonics pinch out to negligible numbers at ~302 m.

Rivernook A bed in outcrop had 22 taxa, four with 20+ specimens whereas subsurface Rivernook A bed had only one taxon with 20+ specimens; planktonics were well represented; Cyclammina species were absent (Taylor 1970 pers. comm.). This was the only one of the faunas that appeared to have greater abundance and diversity in outcrop compared to the bore.

McGowran (1965) examined the Rivernook Member outcrop and combined several samples for an assemblage of 82 taxa, with nine in open nomenclature, including 37% planktonics, 53% cibicidids and rare Cyclammina (1–10). Taylor’s (1971) foraminiferal assemblage from the Rivernook Member outcrop had 46 taxa with two in open nomenclature, nine with 20+ specimens. Eight out of 46 taxa were cibicidids; planktonics were present with three taxa having 20+ specimens; there were no Cyclammina. When comparing the two, Taylor’s (1970 pers. comm., 1971) assemblage appears to be considerably smaller than McGowran’s. Omitting taxa in open nomenclature, only 22 species are common to both authors (McGowran 1965).

Trochocyathus fauna

The Trochocyathus fauna in Latrobe-1 bore from 256–305 m is found in both the Turritella and Trochocyathus beds, and the interval down to the top of the Rivernook fauna at 289.56 m. The fauna has 49 species, of which 14 are single specimen and four are 20+ specimens. Compared to Princetown and Rivernook, the lack of Cyclammina is notable―with only one specimen. The fauna has 25 species that are absent from the Princetown fauna and five missing from the Rivernook fauna. All of these, bar one, Lagena sp., are in very small numbers with 1–5 specimens per species. The composition of the assemblage ranges through 60–70% nodosariids, 40–50% cibicidids, ~20–25% buliminids, varying small numbers of planktonics, particularly around 266.4 m and negligible agglutinated ones; the dominant species is Anomalinoides aff. noblis. The section had 49% core recovery (Taylor 1970 pers. comm., 1971).

The Trochocyathus Bed in outcrop is less diverse (15 species) and less prolific than subsurface with only one species with 20+ specimens (Taylor 1970 pers. comm.). No planktonic species were recorded from the outcrop sample whereas five were recorded in Latrobe-1 bore at 262.74 m (Taylor 1970 pers. comm.). The highest level of agreement between the outcrop sample and Latrobe-1 bore is at 262.74 m with 13 species in common. All the species except one (a single specimen) occur in the Rivernook Fauna.

The Trochocyathus fauna is separated from the older Rivernook and younger Princetown faunas by foraminiferan-free intervals and appears to be a separate ingression, though not reported elsewhere, so apparently localised and minor.

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Princetown fauna

In the Latrobe-1 bore, Taylor designated 207–256 m as the Princetown fauna and described a foraminiferal assemblage at 228.6 m as Princetown type. The assemblage is sparse with little similarity to the Pebble Point and Rivernook faunas (Taylor 1964a, 1965, 1970 pers. comm., 1971). An examination of his biostratigraphic chart (Taylor 1970 pers. comm.) shows the dissimilarity is not in uniqueness of species present but in specimen numbers and proportions of species. The 228.6 m “Princetown type” horizon has nine species, all of which are present in the Trochocyathus fauna, eight in the Rivernook fauna and seven in the Pebble Point fauna. Six of the nine species are represented by single specimens. The author calculates from Taylor’s chart (Taylor 1970 pers. comm.) and cumulative percentages (Taylor 1971) that there are only about 50 specimens in the 228.6 m assemblage. Immediately above and below are 3 m sections with “no fauna found” then small numbers of foraminiferans up to 207 m. By grouping the foraminiferans from 207–228 m and the small (12 species) assemblage at 243.84 m as Princetown fauna there are in all 25 species (half are single specimen occurrences)―two species are absent from the Trochocyathus fauna, three from the Rivernook fauna, and three from the Pebble Point fauna. The composition of the assemblage at 229 m is 70% agglutinated foraminiferans, ~18% cibicidids, ~7% nodosariids, ~5% buliminids, no planktonics; the dominant species is Cyclammina rotundata (Taylor 1970 pers. comm., 1971). The 207–256 m core interval has 49% core recovery (Taylor 1970 pers. comm.).

McGowran (1991) referred to the Princetown Ingression as having relatively good foraminiferal faunas but the Latrobe-1 bore and outcrop assemblages of Taylor (1971) are small. The fauna from the Princetown outcrop yielded only three taxa, all of which are very long ranging in the Latrobe-1 bore (59.44–335 m; Taylor 1970 pers. comm.). The most abundant species in outcrop and subsurface is Cyclammina rotundata). The other two assemblages in outcrop have 2–5 specimens per species, one of which is recorded from Princetown fauna in Latrobe-1 bore (Taylor 1970 pers. comm.). The Princetown fauna is relatively impoverished compared with the other faunas.

Palaeoenvironment

Based on the Latrobe-1 bore foraminiferal faunas, Taylor (1967, 1971) postulated a sequence in which marine conditions were constantly altering due to circulation changes that caused fluctuations in the physico-chemical environment. Alterations in physical barriers resulted in conditions ranging from open marine to stagnant, anaerobic, as well as changing salinities―part of a series of waxing and waning ingressions that decreased in strength upwards and were finally replaced by terrestrial material (Taylor 1967, 1971).

OSTRACODA AS INDICATORS FOR BENTHIC OXYGEN LEVELS

The sensitivity of Ostracoda to their environment and their value for environmental interpretation is well documented (Kornicker 1958; van Morkhoven 1962; Swain 1967; Delorme 1969; De Deckker & Forester 1988; Yassini & Jones 1995; Cronin et al. 1996, 2002; De Deckker 2002; Holmes & Chivas 2002; Smith & Horne 2002) but their potential to monitor the environment and climate is still under-utilised (Smith & Horne 2002).

With the availability of both foraminiferan and ostracod assemblages for comparison, a model for estimating benthic dissolved oxygen levels using ostracods for the Rivernook Member outcrop and Latrobe-1 borehole section was applied and tested against foraminiferan data. In an attempt to quantify levels of dissolved O2 for the marine benthos, Whatley (1991), Lethiers & Whatley (1994, 1995), Whatley et al. (2003) derived, developed and applied a

108 methodology called the Platycopid Signal Hypothesis (PSH) based on the platycopid:podocopid ratios in ostracod assemblages. The underlying premises was that in benthic ostracod assemblages with depleted oxygen levels the suprageneric group, the Platycopina, was often more abundant than the other major group, the Podocopina, that in these O2 depleted assemblages, the Platycopina typically evince high abundance/low diversity, and that the platycopid:podocopid ratios could be used to derive figures for the levels of benthic dissolved O2 (Horne et al. 1990; Whatley 1991, 1995; Boomer & Whatley 1992; Lethiers & Whatley 1994, 1995; Whatley et al. 2003). Earlier, Whatley (1991) had linked this platycopid success to them being filter-feeders (unlike podocopids) and mode of food ingestion provided enhanced water circulation within the carapace.

Lethiers & Whatley (1994) proposed that their anatomical adaptation to the filter-feeder mode of food ingestion provided platycopids with an advantage over the podocopid group in three ways: 1. Opportunity for greater oxygen absorption through the body cuticle. 2. That platycopids (unlike podocopids) incubate their eggs and early stage juveniles within the carapace, thus sharing the benefit of the increased water circulation. 3. The high levels of organic matter usually present in reduced oxygen conditions ensure abundant food supplies for filter-feeders.

Jellinek & Swanson (2003) challenged certain assumptions of the PSH and provided alternative explanations for how platycopid ostracods concentrations could occur in combination with normally occurring short-term, small-scale situations of severely reduced O2 concentrations. They linked the presumed platycopid sedentary lifestyle and their location at or near the sediment-water interface to severely reduced O2 concentrations occurring in this zone (regardless of the dissolved O2 in the overlying seawater), as well as interstitially and within the carapace Jellinek & Swanson (2003). They then suggested that all benthic ostracod taxa would have evolved appropriate survival strategies for these ephemeral events and physiology, that for podocopids their mobility would enable them to relocate during such localised crises, and that such ambulatory activity could flush O2 depleted water out of the carapace Jellinek & Swanson (2003). Their second explanation for platycopid concentrations in O2 again related to a sedentary mode plus the platycopid method of feeding. Based on anatomy, faecal composition and detritus attached to their bodies, Jellinek & Swanson (2003) described platycopids as detritus-feeders not filter-feeders. Consequently, if restricted to areas supplied by a constant rain of appropriately sized particulate organic matter, their occurrence would be patchy, such microenvironments would often be zones of high metabolic activity with correspondingly high O2 consumption resulting in short periods of O2 depletion, unlike the podocopids, the platycopid lack of mobility would again eliminating their ability to relocate.

Swanson et al. (2005) urged caution in using platycopid dominance in fossil ostracod assemblages to assess O2 concentration as the “implied respiratory advantage offered by peculiarities in the platycopid anatomy may result from environmental and reproductive imperatives” as a result of their limited feeding, brooding and movement options.

After its initial widespread acceptance, the PSH has come under increasing scrutiny. Criticism has targeted inadequate referencing, insufficient supporting evidence, lack of transparency in the methodology, that the PSH did not always agree with proxies of other taxa from the same sequence, the basis for the calibration of oxygen levels was not explained nor its precision justified, and that unlike the model, platycopids often do not dominate modern assemblages in OMZs (Brãndao 2008; Gebhardt & Zorn 2008; Brãndao & Horne 2009; Horne et al. 2011).

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In their analysis and assessment of Moroccan Cenomanian ostracod assemblages for use as palaeoenvironmental Gebhardt & Zorn (2008) used established foraminiferan proxies. They found that: unlike the PSH, podocopids always dominated the assemblages in their study section including those with diminished oxygen concentrations; the greatest ostracod abundance was associated with either moderate food supply/sufficient oxygen or high food supply/high oxygen, the ostracods avoiding environments with enhanced organic matter preservation such as occur with oxygen deficiency; and that the thermophylic genus Cytherelloidea was found only in shallow waters, as it was absent in areas of severe O2 deficiency its presence was not an indicator of very low O2, and that it was most frequent during the transition from variable O2 concentrations prior to the onset of permanent O2 deficiency (Gebhardt & Zorn 2008).

Brãndao (2008) described platycopid assemblages in Antarctic waters that varied in abundance from 1.9%–71.4% but, unlike the O2 concentrations predicted by the PSH of <67– >223 μmol/kg (Whatley et al. 2003), his only ranged from 210 to 221 μmol/kg (Brãndao 2008).

Brãndao & Horne (2009) asserted that the PSH was based on too few studies with insufficient supporting evidence given the level of confidence with which the model has been presented and endorsed, that modern observations and experiments on living platycopids have been limited and should only be applied with caution to fossil assemblages and taxa, that widely used terms such as dysoxic or dysaerobic have often been used imprecisely, and that the presentation and interpretation of the data was questionable. Additionally, on the evidence available, Brãndao & Horne (2009) disagreed with the Jellinek & Swanson (2003) opinion of platycopids being detritus-feeders, still accepting them to be filter-feeders.

After commenting on the shortcomings of the PSH, Horne et al. (2011) proposed an alternative model to that of depleted O2 for the existence of platycopid-dominant assemblages in the stratigraphic sequences from which the PSH was derived. Based on their examination of platycopid anatomy, Horne et al. (2011) regarded them to be filter-feeders adapted to food of a particular particle dimension, a size typical of the predominate plankton available in oligotrophic conditions, hence the PSH could be interpreted as an indicator of the same. Against the argument that platycopid abundance is linked to oligotrophic conditions, Ballent & Whatley (2012) give the example of cytherellid super abundance and diversity in reef environments, but surely this counteracts their own argument as reef environments are not typically O2-poor either.

The availability of the Pebble Point, Rivernook and Latrobe-1 ostracod-bearing samples to which foraminiferal studies had already been applied, provided the opportunity to use both microfossil groups to assess the palaeoenvironment and to use the same to assess the reliability of the PSH.

METHODOLOGY

Heywood-10 and Narrawaturk-2 residues collected and processed for foraminiferal studies (Taylor 1964d, 1964d) were re-washed, separated by sieving into course (>1.4 mm), medium (0.3–1.4 mm) and fine (<0.3 mm) fractions, all residue fractions were picked, and augmented with assemblage slides. Taylor used his material to develop foraminiferal assemblages, facies sequence and zonules (Taylor 1964, 1965, 1970 pers. comm., 1971).

The model for assessing benthic oxygen levels according to the percentage of platycopids, the PSH, (Whatley et al. 2003) was applied to ostracod assemblages from the Pebble Point,

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Pember Mudstone, Rivernook and Princetown Members, and the Rivernook A, Trochocyathus and Turritella beds and the findings compared to the foraminiferal data. The calibrated numbers accompanying the qualitative assessments have not been used for the reason already discussed. The benthic dissolved O2 levels indicated by platycopid percentages as proposed by Whatley et al. (2003) were:

% platycopids:podocopids oxygen level < 20% = very high O2 20–30% = high O2 40–60% = medium O2 60–80% = low O2 80–>90% = very low O2

RESULTS: PALAEOENVIRONMENTAL INTERPRETATIONS

Of 26 assemblages from the Pebble Point, Rivernook, Trochocyathus and Princetown (foraminiferal) faunas, 11 had only very small numbers of ostracods, the remaining 15 were used for this study. Of these 15, two were from the Pebble Point fauna (one from Pebble Point Member, one from Dilwyn Mudstone), seven from the Rivernook fauna (all Rivernook Member, three from outcrop, four from Latrobe-1 bore), five from the Trochocyathus fauna (three from the Turritella Bed, one from the Dilwyn Formation and one from the Trochocyathus Bed). Tables 2, 3, & 4 summarise the assemblages and the derived estimates of the benthic dissolved oxygen based on the PSH.

Pebble Point fauna

Samples considered by Taylor (1964a, 1964b, 1964c, 1964d) to be within the Pebble Point fauna come from the Narrawaturk-2, Latrobe-1 and Heywood-10. In Narrawaturk-2 the relevant section, at least 408 m, was barren of ostracods (foraminiferal counts were poor to nonexistent – Taylor 1964c). Two samples from Heywood-10 bore (samples BK-1 and BK-3; 1254–1257 m), and one from Latrobe-1 contained ostracods, all from the Pember Mudstone Member. The two Heywood-10 assemblages were of latest Paleocene age (Taylor 1964a, 1964b, 1964c, 1964d), the Latrobe-1 (Eglington 2006; Sections 2 and 3 herein) was latest Paleocene/earliest Eocene. A large Pebble Point ostracod assemblage, previously described by Neil (1997) from the outcropping Pebble Point Formation, has also been included.

Pebble Point Member, outcrop. This Late Paleocene Pebble Point Formation assemblage described by Neil (1997) is the oldest of the four Pebble Point faunas analysed and by far the largest. From the ostracod taxa represented in his assemblage, Neil (1997) postulated the depositional environment of the marine Pebble Point Formation to be shallow or inner shelf. The single specimen of the warmer water genus Cytherelloidea could have been transported from an upslope habitat.

If the PSH (Whatley et al. 2003) is applied to the group of ~1000 specimens from 44 taxa then platycopids make up 8.4% of the assemblage, based on the model (Whatley et al. 2003) this would indicate a well-ventilated benthos with very high oxygen level. The overall assemblage size and diversity, the high number of Trachyleberids (25%), the presence of the foraminiferan Lagena―a genus adverse to low O2 (McGowran 1965; Taylor pers. comm., 1971), and the absence of the low-oxygen-tolerant foraminiferans Cyclammina or Haplophragmoides in Taylor's sample and their rarity in McGowran’s (McGowran 1965; Taylor pers. comm., 1971) are consistent with well-oxygenated conditions. At this location

111 the Pebble Point Formation marine benthos was apparently cool, well oxygenated, and deeper than the younger Rivernook Member.

Pember Mudstone Member, Heywood-10 bore. Of the two foraminiferal slides from the Pember Mudstone, Heywood-10 bore, the sample BK-1 contained a single specimen, one platycopid, the other, BK-2, contained five platycopids and two podocopids. Three of the five platycopid specimens were Cytherelloidea, a warmer, shallow water genus (Sohn 1962; McKenzie 1974; Gebhardt & Zorn 2008). There is no way of knowing how many ostracods were present in the samples from which these were picked as the residues do not seem to be extant.

Keeping in mind the limitations of the Heywood-10 bore ostracod collection, this small assemblage is characteristic of a warm, shallow marine setting, a possibly poorly oxygenated benthos; the location is well within the Tyrendarra Embayment and is likely to have been a more restricted, marginal marine environment than occurred in the Princetown area. This assessment accords with Taylor’s (1971) interpretation of the palaeontological and sedimentary evidence for the deposition of the Pebble Point Formation in the area of the Heywood-10 bore as marginal marine, probably very close to the shore.

Pember Mudstone Member, Latrobe-1 bore. Extensive picking of the Latrobe-1 Pebble Point (Pember Mudstone) interval produced only four ostracods from 3 samples, no conclusions were drawn by Eglington (2006; Section 3 herein). The rarity of specimens suggests the habitat was either too hostile for ostracod habitation, that there was rapid deposition with a large sediment load, (conditions consistent with a delta-related depositional environment, Holdgate 1981), or that conditions were not suitable for preservation. Examination of the foraminiferans reveals that their abundance and diversity is limited; the small, infrequent numbers of planktonic foraminiferans in the 305.4–339 m interval are characteristic of restricted access to open marine surface waters. The sulphides in some of the residues, the absence apart from one taxon (2-5 specimens) of the low-O2-adverse nodosariid benthic foraminiferan Lagena, and the predominance of the low-O2-tolerant, agglutinated, benthic foraminiferan Cyclammina down to 339 m (Ludbrook 1977; Taylor 1970 pers. comm., 1971) accord with a generally low benthic O2 in a shallow, restricted, marginal marine setting too extreme to support ostracod populations. There were no foraminiferans or ostracods at 310.9 m. This may be due to preservation or environmental factors, or a brief reduction in marine influence may have occurred.

In general, the depositional environment for the Pember Mudstone assemblages from Heywood-10 and Latrobe-1 bores, is one of restricted circulation, with a poorly oxygenated benthos at Latrobe-1, in a warmer, shallow, marginal marine setting, compared to the cooler, deeper, well-oxygenated benthos of the Pebble Point Member in the Princetown area.

Rivernook fauna

The ostracod diversities in two of the three outcrop assemblages were the highest for all of the samples with 8.60 for RIVMcG and 10.00 for RIVIV (Table 5) but platycopid numbers and diversity were low (Table 2). Cytherella postatypica (Section 4 herein) is found in only one of the three samples (five specimens), Cytherelloidea jugifera McKenzie et al. (1991) in two samples, and a possible Cytherella pinnata McKenzie et al. (1993) in one. Based on the PSH, the low platycopid percentages (Table 2) denote benthic O2 levels ranging from medium-high to very high. In Taylor’s outcrop assemblage (Taylor 1970 pers. comm.) only one of the low- O2-adverse Lagena taxon is represented (2-5 specimens), but the low-O2-tolerant foraminiferan Cyclammina is also absent (and rare in McGowran’s, listed as

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Haplophragmoides, McGowran 1965), this supports the proposal that, for at least some of the outcrop strata, the benthos was well-oxygenated. In the bottom ~8.5 m of the Rivernook fauna in Latrobe-1 bore (Eglington 2006, Sections 2 and 3 herein), the specimen numbers were too small for assemblage analysis and core recovery was poor.

Sample/ Spec. Platy. PSH Cyth. Cyc./Hap. Lagena PSH depth nos % O2 level present present present yes/no

Outcrop RIVIV 16 31.0 high med } 1 yes RIVMcG 44 4.5 v. high √ } taxon yes RIVB 44 6.8 v. high √ } 2-5 spec. yes Latrobe-1 53B 292.3 m 29 93.1 v. low √ yes 54 295.35 m 31 80.6 v. low √ yes 54A ~295.96 m 36 83.0 v. low √ √ ? 54B ~296.5 m 58 72.4 low √ √ ? 54C ~297.0 m 3* 0* * √ 54F ~298.5 m 5* 100.0* * √ √ 55 299.62 m 2* 50.0* * √ √ 299.6-304.5 m 5* 0* * √ 56top 304.8 m 2* 0* * √ √ 56A 305.41 m 3* 3* * √

Table 2. Platycopid percentages and O2 levels derived from the PSH for samples from the Rivernook fauna (Rivernook Member and Rivernook A Bed); * = number too small for consideration; ~ approximate position; √ = present, PSH yes/no indicates whether the PSH model is confirmed or contradicted; "?" = denotes comparative data are ambiguous; Cyth. = Cytherelloidea; Cyc./Hap.= Cyclammina/ Haplophragmoides; Lag. = Lagena, numbers after √ are the specimen counts.

At the 301.75–304.8 m interval, planktonic foraminiferans provide evidence for open marine conditions that allowed surface water circulation, but this does not seem to have aided the benthos where virtually all buliminids, nodosariids and cibicidids are absent (although there are 2-5 specimens of one Lagena taxon), Cyclammina is the only agglutinated foraminiferan present (Taylor 1970 pers. comm., 1971). Based on the small ostracod numbers, presence of sulphides and dominance of Cyclammina (Taylor 1970 pers. comm.), it is concluded that during the planktonics flood, the benthos at this location was stagnant, O2-deficient and isolated from surface currents. The planktonics diminish to a low, steady level from 302 m through the rest of the Rivernook Member as surface conditions again became restricted (Taylor 1971).

At ~296.5 m, the lowermost of the top four positions, is the largest Latrobe-1 Rivernook fauna ostracod assemblage, with 58 specimens representing 13 taxa. Of these, two platycopid taxa make up 72.4%, with Cytherella postatypica accounting for 39 of the specimens, applying the PSH (Whatley et al. 2003) this would be interpreted as a low benthic O2 level. The environment at this location was warm, shallow (presence of Cytherelloidea jugifera), restricted/marginal marine. The foraminiferans support the O2 assessment with few planktonics thus there was limited access to open waters, a fairly high proportion of Cyclammina and the dominance of buliminids, nodosariids and cibicidids (Taylor 1970 pers. comm., 1971).

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Through the top 4.2 m of the Rivernook Member from ~296.5–292.3 m (Eglington 2006; Sections 2 and 3 herein), there is a steady decrease in ostracod assemblage size and diversity (Table 5) and an increase in the proportion of platycopids. Applying the PSH (Whatley et al. 2003) this would be interpreted as indicating a drop in dissolved O2 from low at ~296–296.5 m to very low at 292.3–295.4 m. At the top, agglutinated foraminiferans dominate as the effects of the transgression diminish and marine conditions further deteriorate (Taylor 1971).

Although large variations in the taxonomic composition of the ostracod assemblages from the various Rivernook samples has been described (Eglington 2006; Sections 2 and 3 herein; Table 5 this section), another feature now evident is the possibility that the O2 levels of the environments for the outcrop and the subsurface assemblages (Table 2) may have been very different. Based on the PSH (Whatley et al. 2003), and supported by the foraminiferal assemblages, the subsurface O2 levels appear to have been low to very low, and the outcrop levels high-medium to very high. This is not unreasonable with the two locations being nearly 4 km apart in a marginal marine situation where individual local geomorphologic settings and histories could be different. Ostracods in the Rivernook outcrop samples had a higher proportion of carapaces to single valves and far lower juvenile:adult ratios than did Latrobe-1. If the numbers of carapaces were related only to fast burial, preservation of instars would be expected. Their absence, however, may be related to removal of the valves and instars by winnowing― this would be consistent with good bottom-water circulation and ventilation.

Faunal variability in the Rivernook Member is not confined to ostracods. McGowran (1965) commented on the differences in his Rivernook foraminiferal assemblages, but concluded that the cause was most likely to have been either non-uniformity in the sampling methods employed by various collectors, or for preservational reasons. Comparison of his faunal list to that of Taylor (1970) also reveals disparity. That this level of variability is present in both Ostracoda and Foraminifera suggests that the variations McGowran (1965) observed were real, facies-related, and not preservational or methodological.

Although the Rivernook Member represents a significant marine ingression, differences in the composition of the assemblages and of benthic O2 from very high to very low would be characteristic of a marginal marine environment with a high degree of instability and variability of local conditions. Ostracods can be extremely sensitive to changes in substrate, salinity, current velocity, dissolved O2, pH and temperature (Kornicker 1958; Yassini & Jones 1987; Yassini & Wright 1988). Any shifts in freshwater input or placement of sand bars and channels could result in dramatic population changes; numerous studies demonstrate this variability (e.g. Benson et al. 1961; McKenzie 1964; Puri 1966; Swain 1967; Bentley 1988; Yassini & Jones 1995).

In summary, the Ostracoda (Eglington 2006, Sections 2 and 3 herein) imply that the environmental conditions for the Rivernook Member were shallow, warm, marine, (Cytherelloidea's preference for water that is 20–25°C, shallow <100 m; cf. McKenzie 1974; Sohn 1962; Gebhardt & Zorn 2008). Reduced benthic O2 conditions existed at times, particularly in the area of the Latrobe-1 bore Cyclammina present), but not so in the outcrop samples (Cyclammina absent).

The environment was epineritic (Cytherelloidea, Munseyella, “Hermanites”, Xestoleberis), to neritic (Trachyleberis, Neonesidea). Most of the ostracod genera listed are common in, but not exclusive to, these environments. The substrate was stable as ostracods are largely burrowers and not adapted for existence in shifting sands (Kornicker 1958); these strata would

114 not have been part of an active delta system. The differences in assemblage compositions demonstrate the variability of local conditions during the Rivernook Ingression.

Trochocyathus fauna

In the Latrobe-1 bore (Eglington 2006; Sections 2 and 3 herein) three of the six samples from the Trochocyathus fauna (which extends through the Turritella and Trochocyathus beds), had ostracod assemblages with 20+ specimens,; the lowest position within the Turritella Bed at 264.6 m was the most prolific for the entire Paleogene interval with 116 specimens, but also had a very low diversity (Table 5). Applying the PSH (Whatley et al. 2003), the platycopid:podocopid ratios indicate two horizons with low O2, one with medium and two high (Table 3). The O2 appear to fluctuate even within a single unit, for example, the PSH interpretation for the Turritella Bed would be intervals of both high and low O2 levels (Whatley et al. 2003). Cytherelloidea at the base of the Turritella Bed indicates warm, shallow conditions.

Planktonic foraminiferans were very limited in Latrobe-1 and absent in Taylor's outcrop sample (Taylor 1970 pers. comm.). This suggests the marine environment in the area of outcrop was even more restricted than at the bore location.

Sample/ Spec. Platy. PSH Cyth. Cycl./Hap. Lagena PSH depth nos % O2 level present present present yes/no

Trochocyathus Bed 45B 257.86 m 8 25.0 high √ 1 spec. ? Dilwyn Formation 46A 259.38 1* 100.0* * √ 4 taxa 46B 260.6 m 22 45.5 medium Turritella Bed 262.1-262.7 m 9 77.8 low 47A 262. 74 m 27 22.2 high √ √ 4 taxa yes 47B 264.57 m 116 72.4 low √ possibly no

Table 3. Platycopid percentages and O2 levels derived from the PSH for assemblages in Latrobe-1 Trochocyathus fauna; * = number too small for consideration; √ =present, PSH yes/no indicates whether the PSH model is confirmed or contradicted; "?" = denotes comparative data are ambiguous; Cyth. = Cytherelloidea; Cyc./Hap.= Cyclammina/Haplophragmoides; Lag. = Lagena; numbers after √ are the specimen counts.

Princetown fauna

Two horizons in the Princetown fauna of Latrobe-1 bore had sufficiently large ostracod assemblages for the application of the PSH (Whatley et al. 2003), one at 211.23 m and the other at 229.21 m (Table 4). With 40% and 55% platycopids, the PSH readings (Whatley et al. 2003) would be interpreted as high medium and low medium level O2 for the benthos. The assemblage at 229.21 m contained Cytherelloidea which typically inhabits warm, shallow marine conditions. The presence of Cytherelloidea may support the supposition of a moderately oxygenated benthos as a Cenomanian species of Cytherelloidea has been demonstrated to be adverse to severe O2 deficiency (Gebhardt & Zorn 2008).

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The PSH is neither strongly supported by, or in conflict with the foraminiferal data for the 211.23 m assemblage. At 229.21 m arenaceous foraminiferans dominating with cibicidids and nodosariids also well represented, plus a small quantity of buliminids with no planktonics (Taylor 1971). For the foraminiferans it was a restricted, stressed environment (small numbers and diversity dominated by one agglutinated taxon Cyclammina) lacking access to open marine surface waters (absence of planktonics). This finding would suggest that the benthos was perhaps less well oxygenated than the PSH indicates.

Sample/ Spec. Platy. PSH Cyth. Cyc./Hap. Lagena PSH depth nos % O2 level present present present yes/no

40A 211.23 m 10 40.0 high med √ - 43B 229.21 m 38 55.3 low med √ √ 20+ √ 1 ?

Table 4. Platycopid percentages and O2 levels derived from the PSH for assemblages in Latrobe-1 bore Princetown fauna. √ = present; PSH yes/no indicates whether the PSH model is confirmed or contradicted; "?" = denotes comparative data are ambiguous; Cyth. = Cytherelloidea; Cyc./Hap.= Cyclammina/Haplophragmoides; Lag. = Lagena; numbers after √ are the specimen counts.

With further shallowing and deteriorating marine conditions up-section, the ostracod and foraminiferal numbers decline then disappear by 204.22 m (Taylor 1970 pers. comm., 1971). There are at least eight “no fauna found” horizons (Taylor 1970 pers. comm.) from the base of the Princetown fauna to the last sample with foraminiferans― further evidence of fluctuations. In these labile conditions even small changes of seasonality, physical and chemical conditions especially salinity, and supply of terrestrially derived organic matter, would be impacted on the faunas.

Spore/pollen analyses from outcrops of the Pebble Point Formation through the Princetown Member show an up-section warming trend. The first sharp increase in this steady shift from cold to warm climate taxa is seen in the upper Pebble Point/lower Pember Mudstone; the rise is then even, slowing from the Rivernook Member to just below the Turritella Bed. At that point there is a rapid increase, a plateau, then decrease near the base of the Trochocyathus Bed, from whence warming reverts to a steady increase then to another acceleration in the Princetown Member (Harris 1965). These trends conform to the results of this research and to the general conditions prevailing during the PETM and EEOC.

Diversity

The diversity of the larger assemblages was measured using the reciprocal of Simpson's Diversity Index (D) 1 = N(N-1) D ∑ n(n-1) where n = total number of organisms of a particular taxon, N = total number of organisms of all species.

Taking only the assemblages with >15 specimens, the results show the greatest diversity to be from two of the outcropping Rivernook Member samples (8.60 for Riv per McG, 10.00 for RivIV) which is markedly higher than for the same unit subsurface (1.25-4.32). The Princetown and Trochocyathus Faunas average around 5.5 apart from the largest of all the assemblages studied (47B in the Trochocyathus Fauna) which had a very low diversity (2.20).

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Sample Total number Total number Measure of of specimens of taxa diversity Princetown Fauna 40A 211.23 m 10* 7 1.10* 43B 229.21 m 38 7 5.17 Trochocyathus Fauna 45B 257.86 m 8* 4 5.60* 46B 260.6 m 22 6 5.02 860-862' 262.1-262.7 m 9* 2 1.64* 47A 262.74 m 27 7 6.50 47B 264.57 m 116 13 2.62 Latrobe Rivernook Member 53B 292.3 m 29 3 1.25 54 295.35 m 31 6 1.94 54A 295.96 m 36 10 4.32 54B 296.5 m 58 13 2.20 Outcrop Rivernook Member Riv per McG 44 12 8.60 RivB 44 10 4.15 RivIV 16 9 10.00

Table 5. Diversity of the ostracod assemblages from Latrobe-1 borehole and Rivernook Member outcrop using the reciprocal of Simpson's Diversity Index, higher number = greater diversity. Assemblages of < 8 specimens have not been included; * are considered to be too small for discussion.

DISCUSSION

The incomplete stratigraphy of the Paleocene–Eocene Chron 24 interval, within and on the margins of basins, the dearth of deep-sea records, controversy concerning the exact definition and correlation of the Paleocene–Eocene boundary, and shortage of key microfossil groups have presented major impediments to Paleogene environmental studies (Aubrey 1998; Aubrey et al. 1998). In the southeastern Australian Otway Basin, paucity of Early Paleogene outcrops, and poor recovery of calcitic microfossils, have handicapped work on synthesising the palaeoenvironmental and geological history for that region. New faunal assemblages are thus of great value in contributing information for reconstructing its palaeoenvironmental and geological history. The foraminiferal faunas of the Rivernook Member and Pebble Point Formation have been essential for biostratigraphic dating and stratigraphic alignments, for attempting to clarify the Paleocene–Eocene boundary and its associated major environmental phenomenon (the Paleocene–Eocene thermal maximum, PETM), and for describing and analysing the Pebble Point and Rivernook transgressions/ingressions (Taylor 1964a, 1964b, 1964c, 1964d, 1965, 1971; McGowran 1965, 1970, 1991; McGowran et al. 2000). These events were significant features during the development of the southeastern region of Australia resulting from the Gondwana break-up and subsequent growth of the AAG, later to become the Southern Ocean.

To date, the Pebble Point Formation has yielded the only southeast Australian Paleocene ostracods (Neil 1997); two very small assemblages from the Pember Mudstone Member in Heywood-10 bore now add to this knowledge. The Latrobe-1 borehole (Eglington 2006; Section 2 herein) provided the only subsurface Paleogene assemblage, the first recorded from the Dilwyn Formation, and the first description of ostracods from the Rivernook Member. Ostracoda were absent from Baker’s (1950) otherwise detailed list of minerals and fossils of

117 the outcropping unit. Mitchell and Taylor’s foraminiferal assemblage slides contained ostracods but their presence was not reported.

The platycopid model for assessing benthic oxygen

There are valid and well-supported objections to, or qualification of, the PSH (Jellinek & Swanson 2003; Gebhardt & Zorn 2008; Brãndao & Horne 2009; Horne et al. 2011), however in this study in six assemblages the qualitative benthic oxygen estimates derived from the proportions of platycopids in the ostracod assemblages (Whatley et al. 2003) conformed with the foraminiferal data and previous environmental assessments (Harris (1965; McGowran 1965; Taylor 1964, 1965, 1967, 1970 pers. comm., 1971) in six instances, was contradicted in two and ambiguous in three (Tables 2-4).

Low oxygen environment of the Australo-Antarctic Gulf

The generally warm conditions prevailing during the PETM and EECO would have been exacerbated by the restricted, shallow nature of these eastern depositional locations within the far end of the almost completely enclosed AAG, with the warmth of the water decreasing its O2 content. Several other factors, particularly in combination, could account for poor oxygen levels in these deposits, for example, overall distance from the single entry point from the Indian Ocean, weak currents and reduced atmospheric circulation (Exon et al. 2001; Kennett & Exon 2004), very small or virtually zero tidal range (based on similarity in size to the present Mediterranean Sea which has slight tides) thus limiting surface to bottom turnover, restricted shelf (Exon et al. 2004d ) or estuarine location (Arditto 1995), abundant terrestrially-derived organic matter (Baker 1950), high marine biological productivity in eutrophic conditions, or a shallow oxygen minimum zone (OMZ) (Exon et al. 2001; Li et al. 2003; McGowran et al. 2003: Kennett & Exon 2004).

An OMZ extending onto a tranquil continental shelf was described by Exon et al. (2001) from Middle-Late Eocene ODP cores off the west coast of Tasmania, southeast of the Princetown area. Based on the stability of conditions within the eastern end of the Gulf, it is reasonable to assume that the OMZ was in place at least during parts of the Early Eocene. Aided by upslope OMZ movement during transgressions (Whatley 1995) and a low angle of shelf floor, this may have resulted in a reducing environment that was, at times, fairly shallow and/or close to shore. Today, the OMZ in parts of the Atlantic and Pacific oceans occurs anywhere between 100-1000 m (Karstensen et al. 2008), so it is not difficult to envision that, in a warmer, poorly circulating, largely enclosed sea, the OMZ could be considerably higher, especially on a shallow, gently sloping shelf where a small vertical rise would extend a long distance laterally. Another contributing factor to O2 depletion could have been the abundant terrestrially derived plant material in the marine sediments (Baker 1950). Either would explain the reduced O2 and high sulphide content of some of the strata with the low numbers or absence of ostracods. Such corrosive conditions would create an environment unfavourable for vulnerable taxa and some later dissolution of calcitic microfossils. Taylor’s (1965) proposal that destruction of the foraminiferal tests was due to in situ sulphuric acid production may be only part of the explanation for the paucity of calcitic fossils in the marine beds.

CONCLUSION

The results are consistent with a warm, marginal marine setting that ranged from shallow, inner shelf (epineritic) to predominantly estuarine with high organic matter input and fluctuating geomorphologic, physical and chemical conditions, including oxygen levels. The presence or absence of planktonic foraminiferans indicates interspersed periods of open and

118 restricted marine circulation. An on-shelf OMZ may have been present, particularly at the onset of transgressions. While it cannot be ruled out, it would seem unlikely that this OMZ would extend into very shallow, near-shore waters. In such an environment reduced oxygen is more likely to have been caused by local conditions such as the inflowing terrestrial organic matter observed in the sediments (Baker 1950), and to physical barriers (Taylor 1967) such as shifting sand bars closing of channels and resulting stagnation. The area became shallower/more restricted and possibly non-marine, however, non-recovered core intervals make this latter point impossible to state with certainty. Differences in the Rivernook assemblages are explicable in terms of the range of environments occurring in a setting as variable as a marginal marine one, especially if it were estuarine or estuarine-like in function.

The ostracod assemblages have provided useful information concerning the variability of local environmental conditions in these AAG locations. The results obtained for benthic dissolved O2 using the percentage of platycopids in an ostracod assemblage concurred with the foraminiferal data in six instances, was contradicted in two, and ambiguous in a further three (Tables 2-4).

The platycopid model may still prove to be a useful adjunct for environmental analysis though further testing and refining are clearly needed regardless of the cause of the taxon's advantage, in this instance, the PSH for assessing palaeoenvironmental O2 concentrations experienced by these marine fossil assemblages appears to have some merit, though other explanations for the PSH such as an oligotrophic benthos (Horne et al. 2011) cannot be ruled out.

ACKNOWLEDGEMENTS

Grateful thanks for extensive supervisory guidance, support and editorial comment are extended to Kelsie Dadd, John A. Talent and Ruth Mawson of Earth and Planetary Sciences, Macquarie University. The comments and recommendations of the referees Michael Ayress, Alan Lord and Mark Warne are deeply appreciated and grateful thanks extended.

APPENDIX

In his Latrobe-1 bore Geological Survey report, Taylor (1964a) positioned a very small assemblage at 900 ft (274.32 m) but this appears to be an error as his very detailed unpublished biostratigraphic chart (Taylor 1970 pers. comm.) shows an isolated group of 12 taxa at 800 ft (243.84 m), within the Princetown fauna, and “no fauna found” at 900 ft.

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Appendix. Sample positions, platycopid percentages, and O2 levels in Latrobe-1 bore and outcropping Rivernook Member, Early Eocene, Otway Basin, Victoria; * = population too small for analysis.

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SECTION 6

OSTRACODA (CRUSTACEA) OF THE NARRAWATURK FORMATION, EARLY OLIGOCENE, OTWAY BASIN, VICTORIA, AUSTRALIA

COL EGLINGTON

Department of Earth and Planetary Sciences, Macquarie University, Sydney, NSW 2109, Australia. [email protected]

EGLINGTON, C. Ostracoda (Crustacea) of the Narrawaturk Formation, Early Oligocene, Otway Basin, Victoria, Australia

Key words. Ostracoda, Otway Basin, Australia, Oligocene, Ostracoda, Narrawaturk Formation, Nirranda Group, Heywood-10 bore, Victoria, taxonomy.

ABSTRACT

An Early Oligocene marine ostracod assemblage from the Narrawaturk Formation of the Nirranda Group occurs subsurface in the Heywood-10 bore. The sampled assemblage includes 32 taxa in 19 genera from 10 families. Two species and one subspecies are new; eight other taxa are reviewed in further detail, and eight kept in open nomenclature. The new taxa are Aversovalva hasta sp. nov., Xestoleberis heywoodensis sp. nov. and Oculocytheropteron ayressi Majoran, 1997 varius subsp. nov. The assemblage diversity was measured using the reciprocal of Simpson's Diversity Index. The Narrawaturk Formation assemblage had a lower level of diversity and abundance than the Late Oligocene Gellibrand Marl from the same locality, but a higher degree of diversity than an Early Oligocene assemblage from the Port Willunga Formation of South Australia. There was a very low level of commonality between the Narrawaturk Formation compared with the Victorian Oligocene Angahook Member. The assemblage characteristics indicate a well-ventilated inner-shelf environment with some degree of transportation. Although Australian Oligocene Ostracoda have been described from the Eocene/Oligocene boundary in South Australia, from Willunga Embayment cores, and from outcrops in the Aire and Torquay districts of southern Victoria, these specimens are the first described from the Narrawaturk Formation.

INTRODUCTION

Several descriptions and analyses of ostracod faunas from Paleogene surface outcrops in southeastern Australia have been published, but subsurface sections have not received the same treatment. Prior to the 1990s there had been only four published studies on Paleogene Ostracoda of southeastern Australia. These included very brief reports listing species from localities and strata in the Otway Basin (Nadeau 1955); Middle Eocene–Oligocene localities from the coast of Victoria and from Bass and Banks straits (McKenzie 1974); a short report on Eocene-Miocene assemblages from three bores in the Willunga Embayment of the St. Vincent Basin, South Australia (McKenzie 1979) and consideration of the Eocene–Oligocene boundary and Ostracoda as petroleum-potential indicators in the Willunga Embayment (McKenzie & Guha 1987).

From the early 1990s, southeastern Australian ostracods received increased and comprehensive attention. Assemblages studied were the Eocene–Oligocene of the Gull Rock Member of the Blanche Point Formation in the St. Vincent Basin; the Jan Juc Formation in

129 the Otway Basin (McKenzie et al. 1991); the Eocene Browns Creek Clays of the Aire District, Otway Basin (McKenzie et al. 1993); Late Eocene Blanche Point Formation in the St. Vincent Basin of South Australia (Majoran 1995; 1996a); Eocene–Oligocene boundary in the Chinaman’s Gully Formation (Majoran 1996b); cytheropterine Ostracoda of the Port Willunga Formation (Majoran 1997); Oligocene–Miocene palaeobiogeography (including ostracods) of basins in Victoria, South Australia and Tasmania (Neil 1995). The Pebble Point Formation (Late Paleocene) has provided the oldest Cenozoic ostracod assemblage for this region (Neil 1997). Apart from McKenzie (1979), all assemblages were from surface localities.

Palaeontological studies of the Otway Basin subsurface Paleogene have been primarily foraminiferal (Taylor 1963, 1964a, 1964b, 1964c, 1964d,, 1965, 1971a, 1971b; McGowran 1965, 1971, 1989; McGowran et al. 2000; Ludbrook & Lindsay 1969) and palynological: Harris, 1971). Neil (1995) examined the Pember Mudstone for Ostracoda from two bores but without success. The first study of subsurface Paleogene ostracod assemblages was from Latrobe-1 bore (Eglington 2006) of earliest Early Eocene-Early Eocene Wangerrip/Dilwyn Formation. The availability of ostracod-bearing samples from the Heywood-10 bore has provided the opportunity to describe additional Otway Basin subsurface assemblages. This paper is the first to describe an ostracod assemblage from the Narrawaturk Formation.

The Heywood-10 bore is located near the coast of southern Victoria 15 km inland and approximately two kilometres southwest of Heywood township (Fig. 1). The bore, sunk in 1960 for government groundwater exploration, was 1643 m deep.

Fig. 1. Location of Heywood-10 bore, Otway Basin, Victoria, Australia (after Wopfner & Douglas, 1971).

GEOLOGICAL SETTING

The Otway Basin is part of the Southern Rift System (Krassay, Cathro & Ryan 2004) formed by separation of Australia and Antarctica with rifting commencing in the Late Jurassic to Early Cretaceous. Subsidence, marine incursions and the widening of the separation between the two continental blocks resulted in formation of the Australo-Antarctic Gulf. The Otway Basin is a large, broadly northwest-trending trough-like depression located between Lacepede Bay, South Australia, and the eastern side of Port Phillip Bay, Victoria. It includes both on- and offshore regions of Victoria, South Australia and Tasmania. The northern limit is defined by major steepening of the gravity gradient along the northern edge of thick Early Cretaceous–Cenozoic sedimentary rock-packages; its eastern limit is at the Mornington Peninsula-King Island Basement Ridge. The southern boundary is inferred from offshore seismic and drilling information (Wopfner & Douglas 1971; Abele et al. 1993). The main structural components in the eastern Victorian section are the Warrnambool and Otway

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Ranges Highs, and the Port Campbell and Tyrendarra Embayments (Fig. 1). The Heywood-10 bore is situated within the last of these. For this location and period the depositional environment was transgressive marine neritic with minor regressions (Bock & Glenie 1965).

Heywood-10 bore intercepted the following Cenozoic sedimentary units: Heytesbury Group, Nirranda Group (Narrawaturk Formation, Wangoom Sand Member and Mepunga Formation) and the Wangerrip Group (GEDIS; Abele et al. 1976). Only one sample (Table 1: from 371.85 m) was from the Narrawaturk Formation (GEDIS). Gallagher & Holdgate (2000) located its position within the upper Narrawaturk Formation (NF), above the Wangoom Sand Member; the GEDIS biostratigraphic log recorded the presence of Globigerina labiacrassata thus dating it as Early Oligocene (Chaproniere et al. 1996) – P19/20 (Gallagher & Holdgate 2000).

Depth Geological Unit Biostratigraphy Age

Globigerina 335.28 m Gellibrand Marl L. Oligocene euapertura

Narrawaturk Globigerina 371.85 m E. Oligocene Formation labiacrassata

Mepunga Lower Nothofagidites Middle 406.90 m Formation asperus Eocene

Table 1. Heywood-10 Eocene–Oligocene stratigraphy and biostratigraphy (GEDIS; Chaproniere et al. 1996).

The lower sequences Narrawaturk Formation sequences consist of fine-grained shelly siltstone and mudstone, glauconitic in the north, containing both planktonic and benthic foraminiferans. The foraminiferal assemblages accords with a low-energy, marginal marine environment (Holdgate & Gallagher 2003). The upper part of the Narrawaturk Formation has high carbonate content with mudstone grading into marl and marly mudstone, ferruginous sandstone and sandy limestone. Faunal assemblages indicate an inner shelf environment in the north, and mid to outer shelf conditions in the south (Holdgate & Gallagher 2003).

RESULTS: THE OSTRACOD ASSEMBLAGE Methodology

Residues from Heywood-10 bore-core samples collected and processed for foraminiferal studies (Taylor 1964b, 1964d) were rewashed, separated by sieving into course (>1.4 mm), medium (0.3–1.4 mm) and fine (<0.3 mm) fractions, and picked. One sample (54.65 g residue weight after washing) was from the Narrawaturk Formation. The foraminiferal assemblage slide contained ostracods; these are included in the assemblage.

Taphonomy

In the assemblage, the rare instars are almost always carapaces; adult carapaces outnumber disarticulated valves (209:42); fragments are numerous, all indicators of an allochthonous collection.

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Description

The ostracod assemblage of the Narrawaturk Formation consists of 303 specimens in 10 families, 19 genera and 32 taxa (the count includes broken valves and carapaces). At the family level, Bythocyprididae is the most prolific with 82 specimens (27.06%), and Cytheruridae the most diverse with five genera (Fig. 2). 28.1% are single-specimen taxa (Fig. 3); 43.8% had 10 or fewer specimens; the most prolific taxon was Bythocypris sudaustralis with 82 specimens. Abundance in Families 90 Family Genera Specimens % 80

Bythocyprididae 1 82 27.06 70

Cytheruridae 5 55 18.15 60

Xestoleberididae 2 53 17.49 50 Pontocyprididae 3 40 13.2 40 Bairdiidae 2 26 8.58 Abundance Thaerocytheridae 1 16 5.28 30 Trachyleberididae 2 13 4.29 20 Pectocytheridae 1 10 3.3 10 Cytherellidae 1 7 2.31 0

Sigilliidae 1 1 0.33 Sigilliidae

99.99 Bairdiidae

Cytherellidae

Cytheruridae Cytheruridae

Bythocyprididae

Pontocyprididae

Xestoleberididae

Pectocytheridae Thaerocytheridae Trachyleberididae Families Fig. 2. Abundance in ostracod families for Narrawaturk Formation, Heywood-10 bore, Otway Basin, southern Victoria. Figures are actual numbers of specimens.

single specimen 9 taxa 10 9 2-5 specimens 9 taxa 8 7 6 6-10 specimens 5 taxa 5 4

3 Number of taxa Number 11-25 specimens 7 taxa 2 1 0

26-50 specimens 1 taxa 1 2-5 6-10 11-25 26-50 50 + Specimen count categories

50 + specimens 1 taxa

Fig. 3. Composition of the ostracod assemblage, abundance within species and subspecies for Early Oligocene Narrawaturk Formation, Heywood-10 bore.

Eight taxa are in open nomenclature; two new species and one new subspecies are described. The composition of the ostracod assemblage is:

Cytherellidae Cytherelloidea marginopytta McKenzie, Reyment & Reyment, 1991 2 Cytherelloidea jugifera McKenzie, Reyment & Reyment, 1991 5 Bairdiidae

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Neonesidea australis Chapman, 1914) 7 Paranesidea? sp. 19 Bythocyprididae Bythocypris sudaustralis McKenzie, Reyment & Reyment, 1991 82 Sigilliidae Cardobairdia balcombensis Whatley & Downing, 1983 1 Pontocyprididae Propontocypris sp. 1 Argilloecia mesa McKenzie, Reyment & Reyment, 1993 7 Argilloecia sp. aff. A. allungata McKenzie, Reyment & Reyment, 1993 3 Argilloecia spp. 8 Maddocksella tarparriensis McKenzie, Reyment & Reyment, 1993 21 Xestoleberididae Uroleberis minutissima (Chapman, 1926) 14 Xestoleberis basiplana McKenzie, Reyment & Reyment, 1993 3 Xestoleberis heywoodensis sp. nov. 36 Pectocytheridae Munseyella adaluma McKenzie, Reyment & Reyment, 1993 8 Munseyella splendida Whatley & Downing, 1983 1 Munseyella warringa? McKenzie, Reyment & Reyment, 1993 1 Cytheruridae Cytherurinae Hemicytherura fulva McKenzie, Reyment & Reyment, 1993 2 Kangarina wareelacogorra McKenzie, Reyment & Reyment, 1993 7 Eucytherura cameloides McKenzie, Reyment & Reyment, 1993 3 Eucytherura delta McKenzie, Reyment & Reyment, 1993 1 Hemiparacytheridea sp. 1 Cytheropteroninae Oculocytheropteron ayressi Majoran, 1997 varius subsp. nov. 4 Oculocytheropteron microfornix Whatley & Downing, 1983 5 Aversovalva yaringa yaringa McKenzie, Reyment & Reyment, 1993 15 Aversovalva yaringa minor McKenzie, Reyment & Reyment, 1993 4 Aversovalva hasta sp. nov. 13 Trachyleberididae Trachyleberidinae Trachyleberis brevicosta australis McKenzie, Reyment & Reyment, 1991 11 Trachyleberis sp. 1 Pterygocytherideinae Alataleberis johannae McKenzie & Warne 1986 1 Thaerocytheridae Bradleya regularis McKenzie, Reyment & Reyment, 1991 1 Bradleya (Quasibradleya) janjukiana McKenzie, Reyment & Reyment, 1991 15 303 Discussion of the assemblage

Comparison with the Gellibrand Marl. Comparison of the Narrawaturk Formation assemblage with the other Heywood-10 Oligocene assemblage, the Gellibrand Marl (Figs 4 and 5) shows the former is 25% smaller, and has fewer families (10:18), genera (19:33) and species (32:53).

The reciprocal of Simpson's Diversity Index (D): D = ∑ n(n-1) N(N-1)

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[n = total number of organisms of a particular taxon, N = total number of organisms of all species], is used to compare the two assemblages. The value for the Narrawaturk Formation is 9.26 versus 11.36 for the Gellibrand Marl, the higher value confirming the greater diversity in the latter.

20 AG AH 15

Number of % Number specimens 10

Saididae

Krithiidae Sigilliidae

Bairdiidae

Rockalliidae

Cytheruridae Cytherellidae Eucytheridae

Incertae Sedis

Loxoconchidae

Paracyprididae Xestoleberidae

Hemicytheridae

Bythocyprididae

Pontocyprididae Bythocytheridae

Pectocytheridae

Thaerocytheridae Trachyleberididae Families

Fig. 4. Comparison of abundance in families of ostracods from the Early Oligocene Narrawaturk Formation (AH) and Late Oligocene Gellibrand Marl (AG), Heywood-10 bore,Taxa Otway Abundance Basin, Victoria. Numbers are percentages.

25 20

15 AG 10 AH

Number of taxa Number 5

0 1 2-5 6-10 11-25 26-50 50 +

Specimen count categories

Fig. 5. Comparison of abundance of specimens in Gellibrand Marl (AG) and Narrawaturk Formation (AH).

When the two formations are compared at or below genus level, the major similarities are seen in the Bythocyprididae with Bythocypris sudaustralis numbers high in both. The presence of Argilloecia mesa, Argilloecia sp. aff. A. allungata and Maddocksella tarparriensis in Pontocyprididae, Munseyella adaluma, M. splendida and M. warringa? in Pectocytheridae, and Kangarina wareelacogorra, Eucytherura cameloides, Oculocytheropteron ayressi varius, O. microfornix, Aversovalva yaringa yaringa and A. yaringa minor in Cytheruridae. Notable differences in the Gellibrand Marl compared to the Narrawaturk Formation are seen in the diversity and abundance of the Gellibrand Marl Cytherellidae (4 genera, 8 taxa, 46 specimens) and Pontocyprididae (3 genera, 5 taxa. 134 specimens), and the exclusive presence of Hemicytheridae (as Neobuntonia airella, 13.4%). Conversely, in the Narrawaturk Formation, the number of Xestoleberididae (2 genera, 3 species, 53 specimens) vastly exceeds the numbers for the Gellibrand Marl.

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Comparison with the South Australian Port Willunga Formation. These two Heywood-10 assemblages are compared to sample R4 of Majoran (1996a) from the South Australian Early Oligocene, Port Willunga Formation/Ruwarung Member. Calculated at genus level, the Gellibrand Marl (GM) is the most diverse, and the Port Willunga Formation/Ruwarung Member, the least (GM = 8.82; NF = 8.34; R4 = 8.2 reciprocal of Simpson's Diversity Index). With respect to dominant families, each assemblage is very different. In the South Australian assemblage, Bairdiidae are by far the most numerous (31.3%), Cytherellidae second (9.6%). In the Gellibrand Marl Pontocyprididae are the most abundant (32.76%) with Hemicytheridae next (13.45%); in the Narrawaturk Formation, Bythocyprididae dominate (27.06%) over Cytheruridae (18.15%).

Comparison with the Victorian Oligocene Angahook Member. Neil (1995) discussed composition and diversity of ostracod assemblages from the southeast Australian Angahook Member at genus level; two were of Oligocene age (Point Addis and Bells Headland, Torquay Basin). Compositions of these two assemblages differ greatly for the NF and GM – dominant genera being Oculocytheropteron (15.9%) and Bradleya (13.5%) for Point Addis, Quadracythere and Loxoconcha (7.3%) for Bells Headland, compared with the Narrawaturk Formation with Bythocypris (27.1%), Xestoleberis (12.9%), and Gellibrand Marl with Maddocksella (27.9%) and Neobuntonia (13.5%).

Palaeoenvironment

In the Early Oligocene, the Heywood-10 bore location was a shallow marine environment about five kilometres from the shore (Taylor 1971a, 1971b). The assemblage is consistent with an inner shelf environment, as the phytal associates (Neil 1995), Uroleberis and Xestoleberis, account for 17.5% of the specimens and deeper water taxa are absent and the Cytherelloidea taxa are characteristic of a warm, shallow water habitat of less than 100 m (Sohn 1962; McKenzie 1974; Gebhardt & Zorn 2008). The allochthonous characteristics of the assemblage (early instars rare and usually carapaces, adult carapaces outnumbering isolated valves 5:1; and with numerous fragments), indicate transport from the original habitat, presumed to have been closer to the shore. Though the sample contains iron pyrites, given the allochthonous characteristics of the assemblage, the pyrite is assumed to have been transported from a shallower, reducing environment, upslope as the diverse assemblage indicates well-oxygenated bottom waters.

The sample contains iron pyrite, given the allochthonous characteristics of the assemblage, the pyrite is assumed to have been transported from a shallower, reducing environment, upslope.

TAXONOMY

Only taxa requiring discussion have been included in the taxonomy section.

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Plate 1.

A. Neonesidea australis (Chapman, 1914), CRV.

B-F. Paranesidea? sp. B. CRV. C-E. LV internal; detail. F. Detail of surface of Fig. B.

G. Argilloecia sp. aff. A. allungata McKenzie, Reyment & Reyment, 1993, CLV.

H. Cardobairdia balcombensis Whatley & Downing 1983, CRV.

I-J. Xestoleberis basiplana McKenzie, Reyment & Reyment, 1993. I.CRV. J. C dorsal. K-O. Xestoleberis heywoodensis sp. nov. K. C dorsal. L. CLV. M. CRV. N. LV internal. O. LV hinge detail.

P-R. Munseyella adaluma McKenzie, Reyment & Reyment, 1993. P-Q. CLV. R. C dorsal.

S. Propontocypris sp. CLV.

Scale bar = 100 µ, A, B, C, G, H, L, M, N, R, S. Scale bar = 50 µ, D, I, J, K, P, Q. Scale bar = 20 µ, E. Scale bar = 10 µ, F.

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Order PODOCOPIDA Müller 1894 Suborder PODOCOPA Sars 1866 Family BAIRDIIDAE Sars 1888 Neonesidea Maddocks 1969 Neonesidea australis (Chapman 1914) Plate 1A

Bairdia australis Chapman 1914: 31–32, Pl. 6, fig. 7. Neonesidia [sic.] australis – Whatley & Downing 1983: 351, Pl. 1, figs 5–6. Neonesidea australis – Warne 1987: appendix. Neonesidea australis – Warne 1988: 16, Figs 9A–B. Neonesidea australis – McKenzie, Reyment & Reyment 1991: 140, 142, Pl. 1, fig. 5. Neonesidea australis – Yassini, Jones & Jones 1993: 384, Pl. 1, figs 9–10. Neonesidea australis – Ayress 1995: Fig 4.1, Tables 1, 3. Neonesidea australis – Neil 2006: 38, Fig. 2E. Neonesidea aff. N. australis – Eglington 2006: 99, 101, Figs 3L–M.

Remarks. Neonesidea aff. N. australis (Eglington 2006) of ?latest Paleocene/?earliest Eocene to Early Eocene age was so designated because of its considerably smaller size (length, 0.82– 0.85 mm) and minor differences in appearance. These late Early Oligocene specimens are the same size as the Miocene Bairdia australis (Chapman 1914) type material (see also Neil 2006), but smaller than the Late Oligocene specimens of McKenzie et al. (1991) of maximum length 1.21 mm, the Middle Miocene Neonesidea australis adult specimen discussed by Whatley & Downing (1983) at 1.18 mm in length, and Warne’s (1988) late Early Miocene– early Late Miocene of 1.25 mm. That Neonesidea aff. N. australis was ancestral, and that the trend was for size increase through time, is apparent.

Measurements. 2C: length 0.95 mm, height 0.62 mm, breadth 0.5 mm.

Material studied. Seven carapaces: two adults, five juveniles.

Occurrence and age. Narrawaturk Formation: Heywood-10 bore, 371.85 m: Globigerina labiacrassata foraminiferal zone (GEDIS; Taylor 1964b, 1964d), late Early Oligocene (Chaproniere et al. 1996).

Paranesidea Maddocks 1969 Paranesidea? sp. Plate 1B-F

Description. A moderate-sized bairdiid, sub-hexagonal in lateral view. The caudal extension is up-turned, less so in the overlapping left valve. The LV overlaps RV around the entire margin and the LV antero-ventral and antero-dorsal margins bear numerous small spines. The surface is evenly and densely covered with abundant, small, shallow depressions producing a dimpled appearance. Normal pore canals are numerous. The hinge elements are smooth and there is no auxiliary hinge dentition at the anterior or posterior ends.

Remarks. The specimens possess the anterior and posterior marginal denticulation found in Paranesidea but the punctae are finer than typical of the genus. The appearance closely resembles Paranesidea barwonensis Warne (1986), but is larger, and less coarsely punctate. Intermediate forms are common in bairdiids (van den Bold, 1974) as seen in Paranesidea? paucipunctata Titterton & Whatley (1988) which has fine punctae but CMS characteristic of the genus Paranesidea.

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Measurements. Length 0.8–0.9 mm, height 0.5–0.6 mm.

Material studied. Twenty five (predominately adult) carapaces and valves.

Occurrence and age. Narrawaturk Formation: Heywood-10 bore, depth 371.85 m: Globigerina labiacrassata foraminiferal zone (GEDIS), late Early Oligocene? (Chaproniere et al. 1996). Gellibrand Marl: Heywood-10 bore, depth 335.28 m: Globigerina euapertura foraminiferal zone (GEDIS), Late Oligocene (Chaproniere et al. 1996).

Family SIGILLIIDAE Mandelshtam 1960 Cardobairdia van den Bold 1960 Cardobairdia balcombensis McKenzie 1967 Plate 1H

Cardobairdia balcombensis McKenzie 1967: 108–110, Fig. 3 F–H. Cardobairdia balcombensis – Whatley & Downing 1983: 384-385, Pl. 8, figs 1–3. Cardobairdia balcombensis – McKenzie, Reyment & Reyment 1993: 82.

Remarks. This single specimen is of comparable size and displays the RV caudal spine of Cardobairdia balcombensis McKenzie (1967); see also Whatley & Downing (1983). The species was regarded previously as confined to the Middle Miocene (Balcombian) of central coastal Victoria (McKenzie 1967; Whatley & Downing 1983; McKenzie et al. 1993). This occurrence extends the geographic range westward and the age of the species to late Early Oligocene.

Measurements. C: length 0.59 mm, height 0.33 mm, breadth 0.32 mm.

Material studied. One carapace.

Occurrence and age. Narrawaturk Formation: Heywood-10 bore, 371.85 m: Globigerina labiacrassata foraminiferal zone (GEDIS; Taylor 1964b, 1964d), late Early Oligocene (Chaproniere et al. 1996).

Family PONTOCYPRIDIDAE Mȕller 1894 Propontocypris Sylvester-Bradley 1948 Propontocypris sp. Plate 1S

Description. Relatively small, smooth carapace, sub-trapezoidal in lateral view, moderately compressed laterally, maximum height anterior of mid-length; anterior and posterior margins rounded; ventrum slightly inflexed; maximum length near the ventrum; maximum breadth anterior of mid-length. Right valve overlaps left.

Remarks. Propontocypris sp. McKenzie, Reyment & Reyment (1993) is similar in shape to P. sp. but smaller and more elongate; the posterior is more extended and pointed.

Measurements. C: length 0.59 mm, height 0.31 mm, breadth 0.2 mm.

Material studied. One carapace.

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Occurrence and age. Narrawaturk Formation: Heywood-10 bore, depth 371.85 m: Globigerina labiacrassata foraminiferal zone (GEDIS; Taylor 1964b, 1964d), late Early Oligocene (Chaproniere et al. 1996).

Argilloecia Sars 1866 Argilloecia sp. aff. A. allungata McKenzie, Reyment & Reyment 1993 Plate 1G

Argilloecia allungata McKenzie, Reyment & Reyment 1993: 82–83, Pl. 1, Figs 18-19.

Remarks. Argilloecia sp. aff. A. allungata is shorter in length than A. allungata McKenzie, Reyment & Reyment (1993) and its ventral margin is more incurved medially.

Measurements. C: length 0.51 mm, height 0.22 mm, breadth 0.18 mm.

Material studied. Three carapaces.

Occurrence and age. Narrawaturk Formation: Heywood-10 bore, depth 371.85 m: Globigerina labiacrassata foraminiferal zone (GEDIS; Taylor 1964b, 1964d), late Early Oligocene (Chaproniere et al. 1996).

Family XESTOLEBERIDIDAE Sars 1928 Xestoleberis Sars 1866 Xestoleberis heywoodensis sp. nov. Plate 1K-O

Holotype. Plate 1L adult carapace.

Paratypes. Plate 1K adult carapace, 1M adult carapace, 1N adult left valve.

Derivation. From the Heywood-10 bore location.

Type locality. Narrawaturk Formation, Heywood-10 bore, 371.85 m, southern Victoria.

Diagnosis. A medium-sized, sub-triangular Xestoleberis, ovate in dorsal view, with a flattened ventral surface and rounded junction between the lateral and ventral surfaces.

Description. A medium-sized Xestoleberis, sub-triangular in lateral view, ovate in dorsal view, with flattened ventral surface and smooth lateral surface; the characteristic Xestoleberis spot is clearly visible in translucent specimens as is an elongate scar in the antero-dorsal quadrant; LV larger than RV, overlapping it along most of the margin. The dorsum is highly arched with maximum height close to the midline, descending smoothly to the convex anterior margin; behind the dorsal peak the margin descends at a less acute angle to the postero-dorsal area from where it descends steeply to the tightly convexly curved postero- ventral area. The ventral margin of the left valve is predominately straight with a short, slightly inflexed portion at the midpoint; the left valve is straight to very weakly convex. The junction between the lateral and ventral surfaces is rounded. The outline is ovate in dorsal view with maximum breadth medial; junction between the valves sinuous. In ventral view the outline is sub-ovate with the posterior outline more broadly rounded compared to the more pointed anterior; the valve junction lies in a longitudinal depression. Internally, the inner lamella is widest anteriorly and ventrally, narrowest postero-dorsally; anterior vestibule narrow; posterior vestibule unconfirmed due to the shape and position of the ventral margin.

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The observable marginal pore canals are few and straight; normal pore canals scattered. Four elongate central muscle scars occur in a sub-vertical row; frontal scar v-shaped. Hinge merodont.

Remarks. This species closely resembles the Late Eocene Xestoleberis basiplana McKenzie, Reyment & Reyment (1993). It is clearly of the same lineage but larger, and lacks the beak- like anterior marginal overlap; the junction of the lateral and ventral surfaces is rounded compared with the more angular junction in Xestoleberis basiplana. It is slightly larger than X. sp. Whatley & Downing (1983) with a less sharply arched dorsum and more curved postero-dorsal margin.

Measurements. Length 0.44–0.50 mm, height 0.27–0.30 mm, breadth 0.29–0.32 mm. A-1: length 0.4 mm.

Material studied. One juvenile (A-1) and 35 adult carapaces, one opened for internal examination.

Occurrence and age. Narrawaturk Formation: Heywood-10 bore, depth 371.85 m: Globigerina labiacrassata foraminiferal zone (GEDIS), late Early Oligocene? (Chaproniere et al. 1996).

Family PECTOCYTHERIDAE Hanai 1957 Munseyella van den Bold, 1957 Munseyella warringa? McKenzie, Reyment & Reyment 1993 Plate 2B

Remarks. This single specimen has a size and shape comparable to Munseyella warringa McKenzie, Reyment & Reyment (1993). The degraded surface has reduced visibility of the shell features including the ornament.

Measurements. Length 0.35 mm, height 0.20 mm, breadth, 0.16 mm.

Material studied. One carapace.

Occurrence and age. Narrawaturk Formation: Heywood-10 bore, depth 371.85 m: Globigerina labiacrassata foraminiferal zone (GEDIS), late Early Oligocene? (Chaproniere et al. 1996).

Family CYTHERURIDAE Müller 1894 Hemiparacytheridea Herrig 1963 Hemiparacytheridea sp. Plate 2D

Description. Carapace small, heavily calcified, elongate, sub-triangular in lateral view. The antero-dorsal section is elevated and is the area of maximum height; the dorsum is sinuous, terminating at the posterior as part of a large, triangular caudal process; the margin descends from the postero-dorsal area in a long curve to the antero-ventral area. Anterior margin is convex with maximum protrusion forward below the median. Surface ornament minimal, consisting of fine, widely-spaced reticulation most evident on the lateral surfaces of the caudal process, and on or above the postero-ventral hump.

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Measurements. C: length 0.34 mm, height 0.3 mm, width 0.18 mm.

Material studied. One carapace.

Subfamily CYTHEROPTERONINAE Hanai 1957 Oculocytheropteron Bate 1972 Oculocytheropteron ayressi Majoran 1997 varius subsp. nov. Plate 2F-H

Affinity Oculocytheropteron ayressi Majoran 1997: 431-432, fig. 6.16, 20-22.

Holotype. Plate 2H adult carapace.

Paratypes. Plate 2F-G, adult carapaces.

Derivation. Varius (L.) = variant, because of its divergences from O. ayressi ayressi.

Type locality. Narrawaturk Formation, Heywood-10 bore, 371.85 m, southern Victoria.

Diagnosis. A cytheropterine ostracod with similar features to the nominate subspecies but, in dorsal view, the anterior margin projects forward of the otherwise convex anterior outline; the outer posterior termination of the alae possess a small spine. On the posterior margin of the ala, adjacent to the spine, the ala edge protrudes towards the posterior producing a stepped appearance in dorsal view. The surface pattern of reticulation diverges significantly from that of the nominate subspecies.

Description. A medium-sized alate cytheropterine ostracod with sub-rhomboidal outline laterally and spindle-shaped in dorsal view. In lateral view the carapace has a rounded anterior margin below mid-length; it ascends in an almost straight line to the broadly arched dorsum with maximum height at mid-length, then descends to a bluntly terminated caudal process. The caudo-dorsal margin is concave, the caudo-ventral margin straight. The ventral surface is convex, ribbed and pitted. In anterior view, the lateral surfaces curve in an even, concave manner from the dorsum to the outer edges of the alae with very little change in curvature at the ala–carapace interface. In dorsal view, the anterior is acutely pointed, concave for a short distance, then curves in a broad, even, convex arc inwards towards the carapace. At their outer posterior corners, the alae each possess a short, wide spine. The posterior edges of the alae step out towards the rear then run in a virtually straight line to the body of the carapace, meeting it at approximately six-sevenths of full length. The acutely pointed caudal process occupies the remaining length. Midway along the upper surface of each ala is a large, deep depression. The valves are sub-equal with the right valve overlapping the left. The surface is covered with punctae and widely spaced, low, narrow murae, the pattern of this reticulation was consistent across specimens from both strata. CMS visible on external surface of some specimens, consisting of a sub-vertical column of four obliquely inclined rectangular scars; the frontal scar was indistinct. Sightedness could not be confirmed with certainty. As the only valve was a juvenile, internal features for adults could not be described. Sexual dimorphism not observed.

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Plate 2.

A. Munseyella splendida Whatley & Downing, 1983, CRV.

B. Munseyella warringa? McKenzie, Reyment & Reyment, 1993, CRV.

C. Kangarina wareelacoggorra McKenzie, Reyment & Reyment, 1993, CRV.

D. Hemiparacytheridea sp. CRV.

E. Eucytherura delta CRV.

F-H. Oculocytheropteron ayressi varius sub. sp. nov. F. C dorsal. G. CRV. H. C dorsal.

I-K. Oculocytheropteron microfornix Whatley & Downing, 1983. I. C dorsal. J. CRV. K. CLV.

M-P. Aversovalva yaringa yaringa McKenzie, Reyment & Reyment, 1993. M. CLV. N. CRV. O. C anterior. P. C dorsal.

Scale bar = 100 µ, F, G, H, I, J, K, L. Scale bar = 50 µ, A, B, C, D, E, M, N, O, P.

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Remarks. Majoran (1997) described Oculocytheropteron ayressi ayressi Majoran (1997) as fusiform in dorsal view, this implied that the spindle shape tapered at both ends, but this is barely evident at the anterior end as the anterior margin is broadly rounded with only the slightest concavity on either side of the mid-point of the anterior margin. In Oculocytheropteron ayressi varius the anterior margin is acutely pointed and extends well forward. Absence of a sharp, anterior projection, and lack of the terminating ala spur may have resulted from abrasion, but preservation of the fine ornament on Majoran’s material suggests this is not the case. In dorsal view, the alae of Oculocytheropteron ayressi ayressi Majoran (1997) curve inwards and terminate closer to the carapace wall; moreover, the caudal process is broader than in O? ayressi varius. Comparing Oculocytheropteron? ayressi varius to O. aviformum McKenzie et al. (1993), the latter is smaller and lacks the mid ala depression; the alae angle downward more steeply, the dorsal outline is narrower in breadth, and the caudal process less acute.

Measurements. Length 0.50–0.54 mm, height 0.34–0.4 mm, width 0.33–0.35 mm.

Material studied. Four carapaces from the Narrawaturk Formation, two from the Gellibrand Marl.

Aversovalva Hornibrook 1952 Aversovalva hasta sp. nov. Plate 3F-K

Derivation. Hasta = spear (L.), alluding to taxon’s barbed spearhead appearance in dorsal view.

Holotype. Plate 3H, adult carapace.

Paratypes. Plate 3F–G, I–K, 3F adult right valve, 3G adult left valve, 3I–K adult carapaces, 3J adult left valve.

Type locality. Narrawaturk Formation, Heywood-10 bore, 371.85 m, southern Victoria.

Diagnosis. A medium-sized, sub-rhomboidal, unornamented Aversovalva with at least four pairs of marginal denticles on the anterior margin plus well developed alae projecting away from the carapace and terminating with a pronounced central spine giving them a barbed or trident-like appearance in dorsal view. A sinuous riblet extends across the dorsal surface of the alae.

Description. A medium-sized Aversovalva, sub-rhomboidal in lateral view. Maximum height anterior of mid-length, maximum length above the mid-point, maximum width at approximately two-thirds of length. The dorsal margin is broadly convex, descends to a low, rounded postero-dorsal hump, then incurving to the blunt, broad, caudal process. From the base of the caudal process, the margin descends smoothly to the convex ventrum then ascends forming the broad, convex anterior margin with four to five pairs of broad, widely spaced marginal protuberances that give it a serrated appearance. The sharp, anterior edge of the alae arise from a fine ridge originating close to the anterior margin; it then becomes part of the ala

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Plate 3.

A-B. Hemicytherura fulva McKenzie, Reyment & Reyment, 1993, CLV.

C-E. Aversovalva yaringa minor McKenzie, Reyment & Reyment, 1993. C. C dorsal. D. CLV. E. CRV.

F-K. Aversovalva hasta sp. nov. F. RV. G. LV. H. C dorsal. I. C anterior. J. LV internal. K. CRV.

L. Cytherelloidea marginopytta McKenzie, Reyment & Reyment, 1991, FCLV.

M. Alataleberis johannae McKenzie & Warne 1986, CLV.

N. Bradleya regularis McKenzie, Reyment & Reyment, 1991, RV juv.

O. Bradleya (Quasibradleya) janjukiana McKenzie, Reyment & Reyment, 1991, LV.

Scale bar = 100 µ, H, I, L, M, N, O. Scale bar = 50 µ, A, B, C, D, E, F, G, J, K.

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which commences its broad, outward-sweeping curve that is widely hastate in dorsal view with the alae directed outwards away from the body of the carapace. At its extremity, the ala then curves inwards to the wide spinous projection at the centre of its termination. In dorsal view, the broad, hastate appearance is augmented by the trident or barb-like appearance of these alae terminations. The posterior edge of the ala is short and meets the broad carapace body at approximately two thirds of the length. The lateral surface of the posterior portion of the carapace forms a smooth, concave plane through to the end of the caudal process. The surface is predominately smooth, ornament is scarce and composed of a small number of widely spaced, narrow, sinuous riblets on the upper and lower surfaces of the alae and on the antero-ventral area. The left valve overlaps the right forming a broad ridge along the dorsal margin. Internally, the inner lamella is broad without vestibules. The hinge line is straight, the two damaged valves appear to possess smooth median elements; a single, smooth tooth at each end in the right valve is complemented by sockets in the left valve. Large, sparse, normal pores are clearly visible on the internal surfaces of the valves. There is a small vestibule present anteriorly. No other features were noted.

Remarks. The diagnostic criterion for Aversovalva cooperi is “spectacularly developed alae” (McKenzie et al. 1991). Aversovalva hasta is closely related to A. cooperi, having well- developed alae and a mainly unornamented surface, but A. hasta is larger, the terminal spine on the ala much broader and set back within the tip, giving the ala termination a trident-like appearance; the caudal process is more pronounced with an inflexed dorso-caudal section. The alae of Aversovalva cooperi, illustrated in Figs 4a–b of McKenzie et al. (1991), are more extended and narrower, even when the terminal spine is absent (as in the specimen illustrated). If these alar spines were similarly worn off on Aversovalva hasta sp. nov., the alae would be quite short and truncated in appearance. Aversovalva yaringa yaringa (McKenzie, Reyment & Reyment 1993), A. yaringa minor (McKenzie, Reyment & Reyment 1993) and Aversovalve sp. of Neil (1997) are all smaller than A. hasta; in dorsal view their alae are much narrower and close to the body of the carapace; all have ornament of broad punctae. Aversovalva nairana McKenzie, Reyment & Reyment (1993) differs from A. hasta in having punctate surface ornament; outlines of the alae are recurved in dorsal view and have double-pointed terminations.

Measurements. Adults: length 0.41–0.45 mm, height 0.31–0.34 mm, breadth 0.39–0.4 mm.

Material studied. Eleven carapaces, two valves.

Occurrence and age. Narrawaturk Formation: Heywood-10 bore, depth 371.85 m: Globigerina labiacrassata foraminiferal zone (GEDIS), late Early Oligocene? (Chaproniere et al. 1996).

Aversovalva yaringa minor McKenzie, Reyment & Reyment 1993 Plate 3C-E

Cutheropterpon [sic] sp. McKenzie 1979: 93-94, 96, Pl. 1, fig. 15. Aversovalva yaringa minor McKenzie, Reyment & Reyment, 1993: 105, Pl. 6, figs 4, 5.

Description. A small Aversovalva with a broad, shallow ornament and incurving alae in dorsal view.

Remarks. Occurring in both the Gellibrand Marl and Narrawaturk Formation, these specimens are slightly larger than described by McKenzie (1993); it has shorter alae, and the caudal process is proportionally slightly longer.

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Measurements. Length 0.38 mm, breadth 0.21 mm.

Material studied. Four carapaces from Narrawaturk Formation, one from Gellibrand Marl.

Family TRACHYLEBERIDIDAE Sylvester-Bradley 1948 Subfamily PTERYGOCYTHERIDEINAE Puri 1957 Alataleberis McKenzie & Warne 1986 Alataleberis johannae McKenzie & Warne 1986 Plate 3M

Alataleberis johannae McKenzie & Warne 1986: 34-36, Figs 2E, 3A-C, 4A. Alataleberis johannae – McKenzie, Reyment & Reyment 1993: 110, Pl. 6 fig. 19. Alataleberis johannae – Warne 2010: 41-42, Fig. 1A-C, 9E, H.

Remarks. This single Alataleberis specimen’s alate ventral ridges appear to each have at least 6 perforations commencing from the anterior end. These are well expressed on both dorsal and ventral surfaces of the alae though, due to infill, it is not possible to determine whether these penetrate through the alae or are blind depressions. Each ala terminates posteriorly with a single small spine. This specimen is smaller and proportionally higher than Alataleberis johannae (McKenzie & Warne 1986; Warne 2010) and smaller than A. ornithopetrae willungae, A. ornithopetrae ornithopetrae and A. robusta of McKenzie & Warne (1986). Initially placed in open nomenclature, the illustration was subsequently identified by Warne (lit. comm. 2014) as A. johannae. Comparison of the illustrations of this specimen with more recent SCANs (Warne 2010) demonstrates their similarity of appearance in lateral view. The subcentral tubercle is moderately pronounced but is not rounded or as elevated as that of Alataleberis robusta. The dorsal ridges in this specimen have weakly polyfurcate, outwardly angled, posterior terminal spines, between these and the eye tubercles; the RV has three spines and the LV two, though whether the reduced number in the LV was due to damage could not be determined. Alataleberis robusta and A. ornithopetrae ornithopetrae are broader in dorsal view than Alataleberis johannae which also lacks the second taxon’s strong spine below the end of the dorsal ridge. In Alataleberis ornithopetrae willungae the dorsal ridge terminal spine is strongly recurved; in Alataleberis johannae it is outward pointing. Alataleberis miocenica McKenzie & Warne (1986) is slightly smaller, possesses a much more strongly expressed dorsal ridge terminal spine, has fewer or less developed intermediate spines on the dorsal ridge, and the posterior margin ascends at a more obtuse angle to the dorsum.

Measurements. Length 0.85 mm, height 0.43 mm, breadth 0.36 mm.

Material studied. One carapace.

Occurrence and age. Narrawaturk Formation: Heywood-10 bore, depth 371.85 m: Globigerina labiacrassata foraminiferal zone (GEDIS), late Early Oligocene? (Chaproniere et al. 1996).

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CONCLUSION

The single sample from the Narrawaturk Formation provided an ostracod assemblage of 303 specimens across 32 taxa with two new species, Aversovalva hasta sp. nov., Xestoleberis heywoodensis sp. nov., and one new subspecies Oculocytheropteron ayressi Majoran, 1997 varius subsp. nov. From the composition of the assemblage the depositional environment of the Narrawaturk Formation assemblage in the vicinity of the Heywood-10 location is interpreted as warm, shallow marine, inner-shelf, with a well-ventilated benthos. When compared with other Early Oligocene southern Australian marine ostracod assemblages, the Narrawaturk Formation assemblage is more diverse than that of the South Australian Early Oligocene, Port Willunga Formation/Ruwarung Member, and markedly different in composition to an Angahook Member assemblage from the adjacent Torquay Basin (Section 7 herein). There are compositional similarities between this Narrawaturk Formation assemblage and that of the Late Oligocene Gellibrand Marl, also from the Heywood-10 bore, but the former is smaller, less diverse, and the habitat shallower or closer to shore (Section 7 herein).

REPOSITORY

All types and other specimens illustrated in this paper will be deposited in Museum Victoria with the prefix NMV P.

ACKNOWLEDGEMENTS

Grateful thanks for extensive supervisory guidance, support and editorial comment are extended to Kelsie Dadd, John A. Talent and Ruth Mawson of Earth and Planetary Sciences, Macquarie University. The comments and recommendations of the referees Michael Ayress, Alan Lord and Mark Warne are deeply appreciated and grateful thanks extended.

REFERENCES

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succession in the Otway Basin, Southeast Australia. Palaeogeography, Palaeoclimatology, Palaeoecology 156, 19-50. GEDIS Borehole System, Heywood 00010. Geological Survey of Victoria, Department of Manufacturing and Industry Development, Melbourne, Victoria, 11-16. HOLDGATE, G. R. & GALLAGHER, S. J., 2003. Chapter 10 – Tertiary. In Geology of Victoria, W. D. Birch, ed., Geological Society of Australia, Special Publication 23, Victoria, 289-335. KRASSAY, A. A., CATHRO, D. L., & RYAN, D. J., 2004. A regional tectonostratigraphic framework for the Otway Basin. In Eastern Australasian Basins Symposium II, Melbourne, 19-22 September 2004, Adelaide, South Australia, P. J. Boult, D. R. Johns & S. C. Lang, eds, Petroleum Exploration Society of Australia Special Publication (PESA), 97-116. LUDBROOK, N. H., & LINDSAY, J. M., 1969. Tertiary foraminiferal zones in South Australia. In Proceedings of the First International Conference on Planktonic Micro- fossils, Geneva, 1967, vol. 2, P. Brönnimann & H. H. Renz, eds, E.J. Brill, Leiden, 366- 374. MADDOCKS, R. F., 1969. Revision of Recent Bairdiidae (Ostracoda). United States National Museum Bulletin 295, 126 pp. MAJORAN, S., 1995. Late Eocene ostracode biofacies of the Tortachilla Limestone, and the Tuketja Member of the Blanche Point Formation, South Australia. GFF (Geologiska Foreningen, Sweden) 117, 75-80. MAJORAN, S., 1996a. Late Eocene Ostracoda of the Blanche Point Formation, South Australia. Revista Española de Paleontologia 11(1), 18-34. MAJORAN, S., 1996b. Palaeobathymetry of ostracod associations before and after the Chinaman Gully regression (‘Eocene/Oligocene boundary’) in South Australia. Alcheringa 20(4), 247-267. MAJORAN, S., 1997. Cytheropterine Ostracoda in view of the Paleogene Port Willunga Formation, South Australia, and the palaeobathymetrical evolution of the Tasman Basin. Geobios 30(3), 421-435. MCGOWRAN, B., 1965. Two Paleocene foraminiferal faunas from the Wangerrip Group, Pebble Point coastal section, Western Victoria. Proceedings of the Royal Society of Victoria (NS) 79, 9-74, plates 1-6. MCGOWRAN, B., 1971. Chapter 14 – Attempted reconstruction of Tertiary biostratigraphic systems. In The Otway Basin of Southeastern Australia, H. Wopfner & J. G. Douglas, eds, Special Bulletin, Geological Surveys of South Australia and Victoria, 273-281. MCGOWRAN, B., 1989. The late Eocene transgressions in southern Australia. Alcheringa 13, 45-68. MCGOWRAN, B., ARCHER, M., BOCK, P., DARRAGH, T. A., GODTHELP, H., HAGEMAN, S., HAND, S. ., HILL, R., LI, Q., MAXWELL, P. A., MCNAMARA, K. J., MACPHAIL, M., MILDENHALL, D., PARTRIDGE, A. D., RICHARDSON, J., SHAFIK, S., TRUSWELL, E. M. & WARNE, M., 2000. Chapter 9 – Australian palaeobiogeography, the Paleogene and Neogene record. In Memoir of the Association of Australasian Palaeontologists, 23, 405-470. MCKENZIE, K. G., 1967. The distribution of Caenozoic marine Ostracoda from the Gulf of Mexico to Australia. In Aspects of Tethyan Biogeography, C. G. Adams & D. V. Ager, eds, Systematics Association, London, 217-238. MCKENZIE, K. G., 1974. Caenozoic Ostracoda of southeastern Australia with the description of Hanaiceratina new genus. In Geoscience and Man, vol. 6. W. A. van den Bold, ed., B. F. Perkins, series ed., Baton Rouge, 153-182.

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MCKENZIE, K. G., 1979. Appendix 2. Notes on Ostracoda from Willunga Embayment boreholes WLG38, WLG40 and WLG42. In Eocene to Miocene Stratigraphy of the Willunga Embayment, B. J. Cooper, Geological Survey of South Australia, Reports of Investigations No. 50, 90-101. MCKENZIE, K. G. & GUHA, D. K., 1987. A comparative analysis of Eocene/Oligocene boundary Ostracoda from southeastern Australia and India with respect to their usefulness as indicators of petroleum potential. Transactions of the Royal Society of South Australia 111(1), 15-23. MCKENZIE, K. G., REYMENT, R. A. & REYMENT, E. R., 1991. Eocene-Oligocene Ostracoda from South Australia and Victoria, Australia. Revista Española de Paleontologia 6(2), 135-175. MCKENZIE, K. G., REYMENT, R. A. & REYMENT, E. R., 1993. Eocene Ostracoda from the Browns Creek Clays at Browns Creek and Castle Cove, Victoria, Australia. Revista Española de Paleontologia 8(1), 75-116. MCKENZIE, K. G. & WARNE, M. T., 1986. Alataleberis new genus (Crustacea, Ostracoda) from the Tertiary of Victoria and South Australia. Proceedings of the Royal Society of Victoria 98(1), 31-40. NADEAU, B. K., 1955. Australasian Caenozoic Ostracoda. Australian and New Zealand Association for the Advancement of Science, Section C (Geology), 91-94. NEIL, J. V., 1995. Palaeobiogeography of some Oligocene-Miocene ostracode assemblages from southeastern Australia. In Ostracoda and Biostratigraphy – Proceedings of the 12th. International Symposium on Ostracoda, Prague, 1994. A. A. Balkema, Rotterdam, 215-224. NEIL, J. V., 1997. A Late Palaeocene ostracode fauna from the Pebble Point Formation, south-west Victoria. Proceedings of the Royal Society of Victoria 109, 167-197. NEIL, J. V., 2006. Taxonomy of an ostracode assemblage from the Middle Miocene Wuk Wuk Marl, Gippsland, Victoria. Proceedings of the Royal Society of Victoria 118(1), 35-63. SOHN, I. G., 1962. The ostracod genus Cytherelloidea, a possible indicator of paleotemperature. United States Geological Survey Professional Papers 450-D, 162: D144-D147. TAYLOR, D. J., (1963). Latrobe No. 1 biostratigraphic sampling log. Unpublished Report. Geological Survey of Victoria, Department of Manufacturing and Industry Development, Melbourne, 1-7. TAYLOR, D. J., 1964b. Biostratigraphic log Heywood No. 10 bore. Unpublished Report 24.11.64. Geological Survey of Victoria, Department of Manufacturing and Industry Development, Melbourne, 1. TAYLOR, D. J., 1964d. Biostratigraphy Heywood No. 10 bore section. Unpublished Report 26.10.64t. Geological Survey of Victoria, Department of Manufacturing and Industry Development, Melbourne, 1. TAYLOR, D. J., 1965. Preservation, composition, and significance of Victorian Lower Tertiary ‘Cyclammina faunas’. Proceedings of the Royal Society of Victoria, N.S. 78(2), 143-160. TAYLOR, D. J., 1971a. Chapter 10 – Foraminifera and the Cretaceous and Tertiary depositional history. In The Otway Basin of Southeastern Australia, H. Wopfner & J. G. Douglas, eds, Special Bulletin, Geological Surveys of South Australia and Victoria, 217-234, enclosures 10.1 and 10.2. TAYLOR, D. J., 1971b. Chapter 11 – Foraminiferal biostratigraphy of a marginal area of the Otway Basin. In The Otway Basin of Southeastern Australia, H. Wopfner & J. G.

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Douglas, eds, Special Bulletin, Geological Surveys of South Australia and Victoria, 235-239. WARNE, M. T., 1987. Lithostratigraphical associations of the ostracode fauna in the marine Neogene of the Port Phillip and Western Port Basins, Victoria. In Shallow Tethys 2, The Proceedings of the International Symposium on Shallow Tethys 2, Wagga Wagga, 15-17 September 1986, K. G. McKenzie, ed., A. A. Balkema, Rotterdam, Boston, 435-445. WARNE, M. T., 1988. Neonesidea and Bairdoppilata (Ostracoda) from the Miocene of the Port Phillip and Western Port Basins, Victoria, Australia. Alcheringa 12, 7-26. WARNE, M. T., 2010. Review of Alataleberis McKenzie & Warne, 1986 and description of Alatapacifica gen. nov. (Ostracoda, Crustacea) from the Cenozoic of Australia. Alcheringa 34, 37060. WARNE, M. T., 2014. Literary comments supplied by reviewer. WHATLEY, R. & DOWNING, S., 1983. Middle Miocene Ostracoda from Victoria, Australia. Revista Española de Micropaleontologia 15(3), 347-407. WHATLEY, R. C., PYNE, R.S. & WILKINSON, I.P., 2003. Ostracoda and palaeo-oxygen levels, with particular reference to the Upper Cretaceous of East Anglia. Palaeogeography, Palaeoclimatology, Palaeoecology 194, 355-386. WOPFNER, H. & DOUGLAS, J. G., 1971. Chapter 1 – Area and regional setting. In The Otway Basin of Southeastern Australia. H. Wopfner & J. G. Douglas, eds, Special Bulletin, Geological Surveys of South Australia and Victoria, Ministry of Development and Mines, South Australia and Ministry of Mines, Victoria, 17-25. YASSINI, I. & JONES, B. G., 1993. Ostracods from the Gulf of Carpentaria, northeastern Australia. Senckenbergiana Lethaei 73(2), 375-406. YASSINI, I. & JONES, B. G., 1995. Recent Foraminifera and Ostracoda from Estuarine and Shelf Environments on the Southeastern Coast of Australia. University of Wollongong Press, 484 pp.

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SECTION 7

OSTRACODA (CRUSTACEA) FROM THE LATE OLIGOCENE GELLIBRAND MARL, OTWAY BASIN, VICTORIA, AUSTRALIA

COL EGLINGTON

Department of Earth and Planetary Sciences, Macquarie University, Sydney, NSW 2109, Australia. [email protected]

EGLINGTON, C. Ostracoda (Crustacea) from the Late Oligocene Gellibrand Marl, Otway Basin, Victoria, Australia.

Key words. Oligocene, Ostracoda, Gellibrand Marl, Otway Basin, Heytesbury Group, Heywood-10 bore, Victoria, Australia, taxonomy.

ABSTRACT

A Late Oligocene marine ostracod assemblage from the Gellibrand Marl of the Nirranda Group occurs subsurface in the Heywood-10 bore. The sampled assemblage includes 53 taxa from 33 genera across 17 families. Twenty-five taxa were reviewed and 21 placed in open nomenclature. The diverse assemblage indicates that this inner-shelf location was slightly deeper and farther from shore than the Early Oligocene Narrawaturk Formation from the same location. The water was warm, shallow and well-oxygenated. Previous Gellibrand Marl ostracod assemblages have been of Miocene age; these specimens are the first described from the subsurface Oligocene Gellibrand Marl.

INTRODUCTION

There are few studies of Australian marine Oligocene Ostracoda. Crespin (1943) compiled a lengthy list of Oligocene-Miocene ostracods from the Gippsland area of Victoria but did not include illustrations. Not recognizing their unique nature, she assigned most of them to Recent taxa. Some of the dates she suggested have since been revised. McKenzie (1974) undertook a wide-ranging study of Victorian Cenozoic ostracod assemblages, making comparisons primarily at the family level. He erected one new genus, Hanaiceratina, and described several new species; many other new taxa were placed in open nomenclature. He (McKenzie 1974) sampled strata that included the Oligocene Jan Juc Marl, Upper Glen Aire Clays and Calder River Limestone (Late Oligocene: Holdgate & Gallagher, 2003). He was the first to comprehensively use the recently developed SEM techniques for illustrating Ostracoda from the region. He (McKenzie 1979) examined borehole samples from the Willunga Embayment of South Australia and compiled a list of Eocene to Miocene taxa in open nomenclature. McKenzie & Warne (1986) erected a new ostracod genus, Alataleberis, embracing southern Australian Eocene to Oligocene taxa. McKenzie et al. (1991) was a major contribution to ostracod taxonomy for the southern Australian region; it included Late Oligocene strata from Bells Headland, Victoria, and incorporated taxa from his earlier Willunga Embayment report (McKenzie 1979). Neil (1995) published a comparative analysis at genus level of Oligocene to Miocene assemblages from 13 southern Australian localities, two of which were Oligocene. The Eocene–Oligocene boundary was the subject of three ostracod papers: McKenzie & Guha (1987) and Majoran (1996b, 1997). McKenzie & Guha (1987) compared South Australian and Indian assemblages, largely at the family level. Majoran (1996b, 1997) used ostracod associations across the Eocene–Oligocene boundary for

151 bathymetry predictions for the Chinaman Gully and Port Willunga formations in South Australia.

Fig. 1. Location of the Heywood-10 bore, Otway Basin, Victoria, Australia (after Wopfner & Douglas 1971).

The availability of a single Heywood-10 bore sample from the Late Oligocene section of the Gellibrand Marl has provided the first ostracod assemblage of that age from the unit. The McKenzie et al. (1991) and Neil (1995) Gellibrand Marl assemblages are Miocene. The only subsurface Oligocene ostracod assemblage from southern Australia is McKenzie's (1979) from the Willunga Embayment, South Australia.

The Heywood-10 bore is located in the coastal region of southern Victoria, 15 km inland and approximately two kilometres southwest of the town of Heywood (Fig. 1). This government bore, sunk for groundwater exploration in 1960, bottomed at 1643.0 m.

GEOLOGICAL SETTING

The Heywood-10 bore (Fig. 1) lies within the Victorian section of the Otway Basin, one of a series of basins in southern Australia formed during Gondwana rifting (Krassay et al. 2004). The basin is east-west trending, approximately 500 km long, extends laterally both on and off shore, and contains thick Mesozoic and Cenozoic strata (Wopfner & Douglas 1971; Abele et al. 1993; Holdgate & Gallagher 2003). The Heytesbury Group occurs throughout the Otway Basin; it consists of Late Oligocene to Late Miocene carbonate rocks. The basal unit, the Late Oligocene Clifton Formation, consists mainly of limestone, sandy limestone and sandy marl deposited in a relatively high energy, inner-shelf environment that became paralic northwards (Gallagher & Holdgate 2000; Holdgate & Gallagher 2003). It is overlain by the mainly Late Oligocene–Early Miocene Gellibrand Marl, consisting largely of grey marl (Gallagher & Holdgate 2000; Holdgate & Gallagher 2003) deposited in a neritic marine environment during a transgressive phase (Bock & Glenie 1965), its foraminiferal content indicates a low energy environment (Holdgate & Gallagher 2003).

The principal Cenozoic sedimentary units intercepted in the Heywood-10 bore are the: Heytesbury Group (Port Campbell Limestone, Glenample Formation, Gellibrand Marl and Clifton Formation), Nirranda Group (Narrawaturk Marl and Mepunga formations) and the Wangerrip Group (Dilwyn Formation, Pember Mudstone Member, Pebble Point Formation and Timboon Sand Member (Abele et al. 1976; Holdgate & Gallagher 2003). The presence of

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Globigerina euapertura at 335.28 m (GEDIS biostratigraphic log; Gallagher & Holdgate 2000) indicates a Late Oligocene age (Chaproniere et al. 1996).

METHODOLOGY

Nine Heywood-10 residues and slides collected and processed for foraminiferal studies by Taylor (1964b, 1964d) were rewashed, separated by sieving into course (>1.4 mm), medium (0.3–1.4 mm) and fine (<0.3 mm) fractions, and picked. Eight samples produced ostracods; the residues varied between 35 and 80 g. Five samples were from the Gellibrand Marl; only the stratigraphically lowest at 335.28 m (54.65 g) is Oligocene (Table 1). The other Oligocene sample from Heywood-10 bore is from the Narrawaturk Formation (Table 1).

Depth Geological Unit Biostratigraphy Age

58.21 m Port Campbell Ls Orbulina suturalis M. Miocene

122.83 m Port Campbell Ls Globigerinoides sicanus M. Miocene

187.79 m Gellibrand Marl Globigerinoides trilobus L. E. Miocene

229.81 m Gellibrand Marl Globigerinoides trilobus L. E. Miocene

260.60 m Gellibrand Marl Globoquadrina dehiscens E. E. Miocene

300.53 m Gellibrand Marl Globoquadrina dehiscens E. E. Miocene

335.28 m Gellibrand Marl Globigerina euapertura L. Oligocene

371.85 m Narrawaturk Fm Globigerina labiacrassata E. Oligocene

Table. 1. Heywood-10 bore Oligocene–Miocene stratigraphy and biostratigraphy (GEDIS; Chaponiere et al. 1996).

RESULTS

Composition of the ostracod assemblage

Four hundred and nine specimens, including broken valves, were picked. Adult carapaces outnumber valves (217:32); the few juveniles are mostly carapaces. The 409 specimens are from 18 families, 34 genera and 53 taxa. Almost half (43.4%) of all species and subspecies are represented by a single specimen (Fig. 2); a further 43.4% contain 10 or fewer specimens. The most prolific species is Maddocksella tarparriensis with 84 specimens (20.5%), making the Pontocyprididae the most abundant family. Although the Cytheruridae is the most diverse at genus level (five genera), the Cytherellidae with eight species has the highest number of taxa.

Because of inadequate material, 24 taxa are in open nomenclature; eight of these are similar to described species, but possess sufficient variation in morphology to leave some uncertainty as

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160 140 120 100 80

20 0

Saididae

Krithiidae

Bairdiidae

Rockalliidae

Cytheruridae

Cytherellidae Eucytheridae

Incertae Sedis

Loxoconchidae

Xestoleberidae Paracyprididae

Hemicytheridae

Bythocyprididae

Pontocyprididae Bythocytheridae Pectocytheridae

Thaerocytheridae Trachyleberididae Fig. 2. Abundance in families, Gellibrand Marl, Heywood-10 bore, Otway Basin, southern Victoria. Figures are actual numbers of specimens. to precise species attribution. Sixteen are identified to genus level. In most instances, single or very few specimens, made assessment of intra-specific variation problematic, or preclude creation of new species. Table 2 lists the composition of the ostracod assemblage.

Cytherellidae Cytherella sp. aff. C. batei 9 Cytherella aff. C. paranitida Whatley & Downing, 1983 7 Cytherella sp. 3 Platella parapunctata (Whatley & Downing, 1983) 7 Cytherelloidea marginopytta McKenzie, Reyment & Reyment, 1991 1 Cytherelloidea jugifera McKenzie, Reyment & Reyment, 1991 3 Cytherelloidea intermedia (Chapman, Crespin & Keeble, 1928) 8 Geelongella antyx McKenzie, Reyment & Reyment, 1991 8 Bairdiidae Paranesidea? sp. (Section 6 including plate 1B-F herein). 25 Bythocyprididae Bythocypris sudaustralis McKenzie, Reyment & Reyment, 1991 46 Orlovibairdia sp. 1 Cardobairdia? sp. 1 Paracyprididae Paracypris sp. aff. P. bradyi McKenzie, 1967 1 Paracypris sp. 1 Tasmanocypris? sp. 2 Pontocyprididae Propontocypris? sp. 2 Argilloecia mesa McKenzie, Reyment & Reyment, 1993 14 Argilloecia sp. aff. A. allungata McKenzie, Reyment & Reyment, 1993 4 Maddocksella tarparriensis McKenzie, Reyment & Reyment, 1993 84 Maddocksella spp. 30 Saididae Saida sp. aff. S. daisa McKenzie, Reyment & Reyment, 1993 7 Bythocytheridae Sclerochilus sp. 1 Krithiidae

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Krithe postcircularis McKenzie, Reyment & Reyment, 1993 6 Eucytheridae Pseudeucythere pseudosubovalis (Whatley & Downing, 1983) 1 Loxoconchidae Loxoconcha macgowrani McKenzie, Reyment & Reyment, 1991 2 Loxoconcha punctabella McKenzie, Reyment & Reyment, 1991 3 Xestoleberididae Uroleberis minutissima (Chapman, 1926) 6 Xestoleberis noccia McKenzie, Reyment & Reyment, 1993 1 Pectocytheridae Ruggieriella sp. 1 Munseyella adaluma McKenzie, Reyment & Reyment, 1993 2 Munseyella splendida Whatley & Downing, 1983 3 Rockalliidae Rockallia sp. 1 Cytheruridae Cytherurinae Kangarina wareelacogorra McKenzie, Reyment & Reyment, 1993 2 Eucytherura cameloides McKenzie, Reyment & Reyment, 1993 10 Eucytherura horrida McKenzie, Reyment & Reyment, 1993 20 Hemiparacytheridea sp. 1 Cytheropteroninae Cytheropteron sp. aff. C. ruwarungensis Majoran, 1997 1 Oculocytheropteron ayressi Majoran 1997 varius sub. sp. nov. 3 Oculocytheropteron microfornix Whatley & Downing, 1983 7 Aversovalva yaringa yaringa McKenzie, Reyment & Reyment, 1993 7 Aversovalva yaringa minor McKenzie, Reyment & Reyment, 1993 1 Hemicytheridae Neobuntonia airella McKenzie, Reyment & Reyment, 1991 55 Trachyleberididae Trachyleberidinae Acanthocythereis sp. 1 Trachyleberis brevicosta major McKenzie, Reyment & Reyment, 1991 1 Glencoeleberis? thomsoni (Hornibrook, 1952) 1 Oertliellinae Cletocythereis taroona McKenzie, Reyment & Reyment, 1993 3 Thaerocytheridae Bradleya sp. cf. B. regularis McKenzie, Reyment & Reyment, 1991 2 Bradleya (Quasibradleya) momitea McKenzie, Reyment & Reyment, 1993 1 Incertae Sedis Indet. sp. 1 1 Indet. sp. 2 1 409

Table 2. The composition of the ostracod assemblage

Comparison with other assemblages

Comparing the Gellibrand Marl and the Early Oligocene Narrawaturk Formation assemblages from the same location (Section 6 herein), the former is 25% larger, has fewer phytal associates and has more families (18:10), genera (34:19) and species (53:32).

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The reciprocal of Simpson's Diversity Index (D): D = ∑ n(n-1) N(N-1) (n = total number of organisms of a particular taxon, N = total number of organisms of all species), is used to compare the diversity of the assemblages. The value for the Gellibrand Marl is 11.36 versus 9.26 for the Narrawaturk Formation (Section 6 herein), the higher value confirming the greater diversity of the former.

When the two Heywood-10 assemblages are compared at genus level to sample R4 of Majoran (1996a) from the South Australian Early Oligocene, Port Willunga Formation/Ruwarung Member, the Gellibrand Marl (GM) is the most diverse, and the Port Willunga Formation/Ruwarung Member, the least (GM = 8.82; NF = 8.34; R4 = 8.2 reciprocal of Simpson's Diversity Index).

The three assemblages are very different at the family level. In the Gellibrand Marl Pontocyprididae are the most abundant family (32.76%) with Hemicytheridae next (13.45%); in the Narrawaturk Formation, Bythocyprididae dominate (27.06%) over Cytheruridae (18.15%); and in the South Australian assemblage, Bairdiidae are by far the most numerous (31.3%) with Cytherellidae second (9.6%).

Palaeoenvironmental interpretation

The environment of this assemblage was off-shore (the presence of Bythocyprididae) with a well-oxygenated benthos as indicated by the diversity of the assemblage. The smaller percentage of phytal associates (Loxoconcha, Uroleberis and Xestoleberis = 2.9%) and Hemicytheridae (Neobuntonia 13.45%) plus the appearance of Krithiidae (Krithe postcircularis) suggests that there had been a moderate increase in depth compared to the Early Oligocene Narrawaturk Formation (Section 6 herein) at this same site. The shallower- water families seen down section are still very evident (Hemicytheridae, Bairdiidae, Xestoleberididae, Loxoconchidae = 22.5%), and there is an absence of any truly deep or cold water taxa. Taylor (1971) inferred the Late Oligocene Heywood-10 location to be an open marine environment approximately 16 km seaward of the coast, the absence of the colder, deeper water taxa indicate that it was probably deeper, mid-shelf (Ayress lit. comm. 2014), part of a wide shelf in this northern region of the Australo-Antarctic Gulf.

With adult carapaces outnumbering valves (217:32), and the few juveniles being mostly carapaces, this assemblage is presumed to be allochthonous, the warmer, shallower-water taxa possibly were transported downslope.

TAXONOMY

Only taxa with features requiring discussion have been included in the taxonomy section.

Order PODOCOPIDA Müller 1894 Suborder PLATYCOPA Sars 1866 Family CYTHERELLIDAE Sars 1866 Cytherella Jones 1849

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Cytherella sp. aff. C. batei Eglington sp. nov. (Section 4 herein) Plate 1F-G

Affinity Cytherella batei Eglington sp. nov. (Section 4 herein).

Remarks. Smooth, ovate Cytherella with a very narrow flattened marginal rim and LV>RV. Females in dorsal view are somewhat wedge-shaped rather than ovate, but not as markedly so as in C. batei (Section 4 herein). Cytherella atypica Bate (1972) lacks the flattened marginal rim and females are ovate in dorsal view. Cytherella postatypica (Section 4 herein) is ovate in dorsal view; in lateral view the dorsum is more highly arched.

Measurements. Adults: length 0.85–0.89 mm, height 0.52–0.58 mm, breadth 0.3–0.33 mm.

Material studied. Nine specimens including adults, juveniles and valve fragments.

Occurrence and age. Gellibrand Marl: Heywood-10 bore, depth 335.28 m: Globigerina euapertura foraminiferal zone (GEDIS), Late Oligocene (Chaproniere et al. 1996).

Cytherella aff. C. paranitida Whatley & Downing 1983 Plate 1C-E

Affinity Cytherella paranitida Whatley & Downing 1983: 385, Pl. 8, figs 4, 5. Cytherella paranitida – Neil 2006: 37, Fig. 3B.

Description. Moderately large Cytherella, sub-rectangular in lateral view with sub parallel dorsal and ventral margins, convex anterior and posterior margin, and concave dorsal and ventral margins. The marginal rim has a narrow, flattened zone inside the edge of the margin, widest from the antero-dorsal to postero-dorsal areas. Lateral surface smooth, slightly depressed medially, coinciding with the CMS. Right valve overlaps left. There are numerous small punctae on the posterior surface and fine reticulation on the marginal rim. This latter feature is particularly well developed along the anterior margin.

Remarks. Cytherella aff. C. paranitida has a concave dorsum compared to the sinuous convex dorsum of Cytherella paranitida Whatley & Downing (1983). The size is comparable to Neil's (2006) specimens; it displays the anterior and posterior marginal reticulation mentioned by him.

Measurements. FC: length 0.80 mm, height 0.46 mm.

Material studied. Five carapaces, two valves, both sexes represented.

Occurrence and age. Gellibrand Marl: Heywood-10 bore, depth 335.28 m: Globigerina euapertura foraminiferal zone (GEDIS), Late Oligocene (Chaproniere et al. 1996).

Cytherella sp. Plate 1A-B

Description. A moderately large Cytherella, sub-rectangular in lateral view with anterior outline evenly convex, dorsal and ventral margins parallel, and the postero-dorsal margin descending vertically to the mid posterior margin then angling forward to meet the postero-

157

Plate 1.

A-B. Cytherella sp. A. FRV. B. FRV.

C-E. Cytherella sp. aff. C. paranitida Whatley & Downing, 1983, FCRV. C. FCRV. D. Detail posterior surface. E. Detail anterior surface.

F-G. Cytherella sp. aff. C. batei sp. nov. F. FRV. G. MLV.

H. Cytherelloidea intermedia (Chapman, Crespin & Keeble, 1928), MC dorsal. I. Platella parapunctata (Whatley & Downing, 1983), CFRV. J. Cytherelloidea jugifera McKenzie, Reyment & Reyment, 1991, RV. K. Cytherelloidea intermedia (Chapman, Crespin & Keeble, 1928), FRV. L. Cytherelloidea jugifera McKenzie, Reyment & Reyment, 1991, RV. M. Cardobairdia? sp. CRV. N. Paracypris sp. CRV. O. Paracypris sp. aff. P. bradyi, McKenzie, 1967, CRV. P-Q. Tasmanocypris? sp. CRV. R. Argilloecia sp. aff. A. allungata McKenzie, Reyment & Reyment, 1993,CLV. S. Sclerochilus sp. T. Propontocypris? sp. CLV.

Scale bar = 100 µ, A, B, C, F, G, H, I, J, K, L, M, O, P, Q, R, T. Scale bar = 50 µ, E, N, S. Scale bar = 20 µ, D.

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ventral section. Maximum height anterior of the median; maximum length just above the median. Twin brood chambers are very evident. In these three right valves there is a continuous, broad, flattened area or rim around the entire margin. Surface smooth with no evidence of micropunctae. The CMS appear to be of regular pinnate form. Internally, these RVs display the hinge and valve margin structure characteristic of the larger valve.

Remarks. The sub-rectangular shape is similar to that of Cytherella sp. Eglington (2006), but the latter is smaller and lacks the continuous flattened marginal rim. The sub-rectangular shape is also reminiscent of Cytherella paranitida Whatley & Downing (1983) but there is no evidence of micropunctae.

Measurements. RVFs: length ~ 0.82 mm, height 0.5 – 0.53 mm.

Material studied. Three damaged adult right valves, two clearly females.

Occurrence and age. Gellibrand Marl: Heywood-10 bore, depth 335.28 m: Globigerina euapertura foraminiferal zone (GEDIS), Late Oligocene (Chaproniere et al. 1996).

Cytherelloidea Alexander 1929 Cytherelloidea intermedia (Chapman, Crespin & Keeble 1928) Plate 1H, K

Cytherella intermedia Chapman, Crespin & Keble 1928: 129–130, Figs 69a, 69b. Cytherelloidea intermedia – Crespin 1943: 100. Cytherelloidea intermedia – McKenzie 1974: 166, Pl. 1.2. Cytherelloidea intermedia – Whatley & Downing 1983: 386, Pl. 8, figs 12–15. non Cytherelloidea cf. intermedia – McKenzie, Reyment & Reyment 1991: 140, Pl. 1.9 [is C. jugifera McKenzie, Reyment & Reyment 1991].

Description. A moderately large Cytherelloidea, sub-rectangular in lateral view with anterior margin evenly convex, dorsal and ventral margins inflexed, and postero-dorsal margin broadly pointed medially. Sulcus deep and wide; inside of margin giving a bulging appearance to the broad marginal zone. Maximum height anterior of the median; maximum length medial. Fine reticulation visible on marginal protrusions.

Remarks. Cytherelloidea intermedia (Chapman, 1928) has previously been reported from Middle Miocene (Balcombian) strata of southern Victorian (Chapman et al. 1928; McKenzie 1974; Whatley & Downing 1983). This occurrence extends the range of the species back to the Oligocene. The specimens are larger than the Miocene material and less wide, with anterior marginal zone narrower, thinner, and protruding, but in all other respects comparable. The author has obtained specimens of Cytherella intermedia of the same size as these adult female valves from the Fishing Point Marl – equivalent to the lower Gellibrand Marl (Holdgate & Gallagher 2003) at Castle Cove, Victoria. The form identified as Cytherelloidea cf. intermedia McKenzie, Reyment & Reyment (1991) in the author's opinion is C. jugifera McKenzie, Reyment & Reyment (1991).

Measurements. FRVs: length ~ 0.89–92 mm, height 0.55–0.58 mm. MC: length ~ 0.88 mm, height 0.52 mm, breadth 0.36 mm.

Material studied. Eight specimens including adult and juvenile carapaces.

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Occurrence and age. Gellibrand Marl: Heywood-10 bore, depth 335.28 m: Globigerina euapertura foraminiferal zone (GEDIS), Late Oligocene (Chaproniere et al. 1996).

Cytherelloidea marginopytta McKenzie, Reyment & Reyment 1991 Plate 4G-H

Cytherelloidea sp. McKenzie 1979: 93-94, Pl. 1, fig. 6. Cytherelloidea marginopytta McKenzie, Reyment & Reyment 1991: 140, Pl. 2, fig. 1, Pl. 10, figs 2, 3. Cytherelloidea marginopytta – McKenzie, Reyment & Reyment 1993: 79, 142, Pl. 1, fig. 10. Cytherelloidea marginopytta – Neil 1997: 170, Figs 4A, 4B.

Affinities Cytherelloidea marginopytta? – Majoran 1995: Fig. 3a, Appendix 1, Table. Cytherelloidea marginopytta – Majoran 1996b: Table 2, Appendix 1.

Remarks. This extremely ornate Cytherelloidea displays four orders of ornament. The coarsest ornament is a pair of broad, well defined ridges –– the ventral ridge, running from the lowermost brood pouch, swells to the antero-ventral area; the ridge from the uppermost brood pouch to the anterior incorporates the deep CMS depression. Much of the surface, including the ridges and marginal areas, has a reticulate system of low, sharp murae. On the sides of the ridges and in the depressions of this network are broad, deep punctae that give the species its distinctive, pitted appearance. Micropunctae are superimposed densely over the entire surface not occupied by the course punctae.

Measurements. FC: length 0.80 mm, height 0.45 mm.

Material studied. One adult female carapace.

Occurrence and age. Gellibrand Marl: Heywood-10 bore, depth 335.28 m: Globigerina euapertura foraminiferal zone (GEDIS), Late Oligocene (Chaproniere et al. 1996).

Platella Coryell & Fields 1937 Platella parapunctata (Whatley & Downing 1983) Plate 1.I

Cytherella parapunctata Whatley & Downing 1983: 386, Pl. 8, figs 9-11. Platella sp. McKenzie, Reyment & Reyment 1993: 78, Pl. 1, fig. 6.

Remarks. Though the punctae in the central area of the figured male carapace are smaller than those in the illustrations in Whatley & Downing (1983) and McKenzie, Reyment & Reyment (1993), the configuration is similar. The punctae on the female carapaces are coarser.

Measurements. FCs: length 0.78–0.80 mm, height 0.41–0.42 mm. MCRV: length 0.72 mm, height 0.4 mm.

Material studied. Seven specimens, both sexes represented.

Occurrence and age. Gellibrand Marl: Heywood-10 bore, depth 335.28 m: Globigerina euapertura foraminiferal zone (GEDIS), Late Oligocene (Chaproniere et al. 1996).

160

Family BYTHOCYPRIDIDAE Maddocks 1969 Orlovibairdia McKenzie 1978 Orlovibairdia sp. Plate 3P

Description. A single, elongate, adult carapace with surface covered with fine punctae; antero-ventral and postero-ventral margins bear spines; dorsal margin hemi-hexagonal in lateral view; ventral margin inflexed.

Remarks. Orlovibairdia sp. has similar punctate ornament to McKenzie’s (1974) Bairdia aff. angulata (Brady 1870) but in the present specimen the ornament is less developed, the posterior marginal denticles do not extend above the caudal process, the postero-dorsal margin is concave not convex, the antero-dorsal margin is longer, descending from the dorsum at a steeper angle and meeting the anterior margin much lower down. Orlovibairdia mooraboolensis Warne (1990) has a smoothly convex dorsal margin. Orlovibairdia sp. McKenzie et al. (1991) is larger, higher and the postero-dorsal margin descends more steeply than in this species. Orlovibairdia? sp. McKenzie et al. (1991) has much larger marginal denticulation. Orlovibairdia sp. McKenzie et al. (1993) is of similar size but is less inflexed ventrally, does not possess an upturned caudal process, has minimal marginal denticulation, and does not appear to have surface punctae. Orlovibairdia cf. arcaforma Swanson (1979, in Yassini & Jones 1995) has a straighter dorsal margin, larger punctae and more robust marginal denticulation.

Measurements. Adult C: length 0.55 mm, height 0.3 mm.

Material studied. Single adult carapace.

Occurrence and age. Gellibrand Marl: Heywood-10 bore, depth 335.28 m: Globigerina euapertura foraminiferal zone (GEDIS), Late Oligocene (Chaproniere et al. 1996).

Family SIGILLIIDAE Mandelshtam 1960 Cardobairdia van den Bold 1960 Cardobairdia? sp. Plate 1M

Remarks. A smooth carapace, ovate in lateral and dorsal views, with left valve overlapping right around the entire margin; caudal spine lacking. No CMS or other internal features observable. This single specimen is similar in shape, but larger than, Cardobairdia sp. McKenzie et al. (1993).

Measurements. C: length 0.48 mm, height 0.3 mm, breadth 0.21 mm.

Material studied. One carapace.

Occurrence and age. Gellibrand Marl: Heywood-10 bore, depth 335.28 m: Globigerina euapertura foraminiferal zone (GEDIS), Late Oligocene (Chaproniere et al. 1996).

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Family PARACYPRIDIDAE Sars 1923 Paracypris Sars 1866 Paracypris sp. aff. P. bradyi McKenzie 1967 Plate 1.O

Affinities Paracypris bradyi McKenzie 1967: 64, Fig 2d. Paracypris bradyi – Hartmann 1981: 128. Paracypris bradyi – Yassini & Jones 1987: 831, Fig. 5.14. Paracypris bradyi – Yassini & Jones 1995: 309, Figs 100-101. Paracypris sp. Eglington 2006: 97, Figs 3E-F.

Remarks. Smooth, elongate, sub-triangular Paracypris with rounded anterior margin ascending to maximum height antero-dorsally, descending in a broad curve to the postero- dorsal area then in an almost straight line to the sub-acuminate posterior. Ventral margin inflexed. Paracypris sp. aff. P. bradyi is smaller and less elongate than P. bradyi McKenzie (1967) when compared to the original illustration, though when compared to P. bradyi (Yassini & Jones 1995), similarity in shape is more evident. This species lacks the dorsal outline angularity of Paracypris sp. Eglington (2006).

Measurements. C: length 0.6 mm, height 0.26 mm.

Material studied. One carapace.

Occurrence and age. Gellibrand Marl: Heywood-10 bore, depth 335.28 m: Globigerina euapertura foraminiferal zone (GEDIS), Late Oligocene (Chaproniere et al. 1996).

Paracypris sp. Plate 1N

Paracypris sp. Eglington 2006: 97, Figs 3E-F.

Remarks. Smooth, sub-triangular Paracypris with straight dorsum falling towards anterior and posterior. The antero-dorsal, mid-dorsal and postero-dorsal margins are each one-third of the length. Anterior margin rounded, ventral margin weakly inflexed, posterior margin sub- acuminate. Maximum height approximately one-third of length. Because of its thin shell and no apparent vestibules visible through the translucent valves, the specimen is assumed to be juvenile. Based on the overall shape, this appears to be the same species as Paracypris sp. Eglington (2006) of the Late Paleocene?–Early Eocene for which there was only one broken adult valve. In Paracypris bradyi McKenzie (1967) the maximum height is farther forward, the ventrum more strongly inflexed, and the angled descent of the dorsum to the posterior is farther back. The Late Eocene Paracypris eocuneata (Hornibrook 1952 in Ayress 1995) from New Zealand has a similar dorsal margin divided into three virtually straight sections, but the posterior section is much more extended, forming a more acutely angled posterior termination than in Paracypris sp.

Measurements. C juv: length 0.39 mm, height 0.18 mm. C juv: length 0.47 mm, height 0.23 mm.

Material studied. One juvenile carapace.

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Occurrence and age. Gellibrand Marl: Heywood-10 bore, depth 335.28 m: Globigerina euapertura foraminiferal zone (GEDIS), Late Oligocene (Chaproniere et al. 1996).

Tasmanocypris McKenzie 1979 Tasmanocypris? sp./spp. Plate 1P-Q Affinity Tasmanocypris? latrobensis Eglington 2006: 97-98, Figs 3G-I.

Remarks. Smooth, sub-triangular paracypridids with maximum height at the median. The two carapaces may be the same species but the larger is deformed by crushing. It is not clear if the smaller is juvenile. They are similar to Tasmanocypris? latrobensis Eglington (2006) but with a smaller height proportional to length.

Measurements. C: length 1.01 mm, height 0.41 mm. C: length 0.8 mm, height 0.32 mm.

Material studied. Two carapaces.

Occurrence and age. Gellibrand Marl: Heywood-10 bore, depth 335.28 m: Globigerina euapertura foraminiferal zone (GEDIS), Late Oligocene (Chaproniere et al. 1996).

Family PONTOCYPRIDIDAE Müller 1894 Propontocypris Sylvester-Bradley 1948 Propontocypris? sp. Plate 1T

Description. Relatively small, smooth carapaces, sub-triangular in lateral view, moderately compressed laterally, with arched dorsum with maximum height slightly anterior of median; ventrum with rounded anterior and posterior, slightly inflexed. Maximum length below the median; maximum breadth anterior of the median.

Measurements. C: length 0.57 mm, height 0.33 mm, breadth 0.19 mm.

Material studied. Two juvenile carapaces, both presumed juveniles.

Occurrence and age. Gellibrand Marl: Heywood-10 bore, depth 335.28 m: Globigerina euapertura foraminiferal zone (GEDIS), Late Oligocene (Chaproniere et al. 1996).

Argilloecia Sars 1866 Argilloecia sp. aff. A. allungata McKenzie, Reyment & Reyment 1993 Plate 1R

Argilloecia allungata McKenzie, Reyment & Reyment, 1993: 82-3, Pl. 1, figs 18-19.

Remarks. Argilloecia sp. aff. A. allungata displays a more incurved ventral margin medially than is seen in A. allungata McKenzie, Reyment & Reyment (1993) but to a lesser degree than in specimens from the earlier Narrawaturk Formation.

Measurements. Length 0.52 – 0.58 mm, height 0.20 – 0.22 mm.

Material studied. Four carapaces.

163

Plate 2.

A-B. Loxoconcha mcgowrani McKenzie, Reyment & Reyment, 1991. A. FCRV. B. MCRV. C-D. Loxoconcha punctabella McKenzie, Reyment & Reyment, 1991. C. FCRV. D. MCLV. E. Saida sp. aff. S. daisa McKenzie, Reyment & Reyment, 1993, LV. F. Munseyella splendida Whatley & Downing, 1983, CLV. G-H. Munseyella adaluma McKenzie, Reyment & Reyment, 1993. G. CRV. H. CLV. I. Munseyella splendida Whatley & Downing, 1983, CRV. J. Rockallia sp. CRV. K. Kangarina wareelacogorra McKenzie, Reyment & Reyment, 1993, CRV. L. Eucytherura cameloides McKenzie, Reyment & Reyment, 1993, CLV. M-N. Hemiparacytheridea sp. detail and CLV (Section 6 herein). O. Eucytherura horrida McKenzie, Reyment & Reyment, 1993, CLV. P. Hemiparacytheridea sp. C dorsal. Q. Eucytherura cameloides McKenzie, Reyment & Reyment, 1993, C dorsal. R. Eucytherura horrida McKenzie, Reyment & Reyment, 1993, C dorsal.

Scale bar = 100 µ, A, B, D, J. Scale bar = 50 µ, C, E, F, G, H, I, K, L, N, O, P, Q, R. Scale bar = 20 µ, M.

164

Occurrence and age. Gellibrand Marl: Heywood-10 bore, depth 335.28 m: Globigerina euapertura foraminiferal zone (GEDIS), Late Oligocene (Chaproniere et al. 1996).

Family SAIDIDAE Aranki, McKenzie, Reyment & Reyment 1992

The genus Saida Hornibrook (1952) was assigned to incertae sedis by its author and subsequent workers (Benson et al. 1961; Swanson 1969) until tentatively positioned in the family Cytheruridae?, subfamily Cytherurinae by Grȕndel in 1969 (Wouters 2007). McKenzie (1974) was the first to suggest tentative placing of the genus in the Cytherinae (Family Cytheridae Baird, 1850); this was supported by later authors (Neale 1975; Whatley & Downing 1983; McKenzie et al. 1991, 1993). Aranki et al. (1992) created the monotypic subfamily Saidinae and added much needed detail to the description of the type genus, Saida Hornibrook (1952). The subfamily was raised to family status by Wouters (2007) and its taxonomic position discussed, assisted by the addition of a new Cretaceous–Recent genus, Saidella Wouters (2007). The described soft anatomy of Saidella gushikamiensis (Nohara 1987), the type species for this new genus, has greatly assisted in the taxonomic process.

Subfamily SAIDIINAE Aranki, McKenzie, Reyment & Reyment 1992 Saida Hornibrook 1952 Saida sp. aff. S. daisa Plate 2E

Affinities Cythere torresi (Brady 1880): 67-68, Pl. 19, figs 8a-c. Saida truncala Hornibrook 1952: 67, Pl. 18, figs 290-292. Saida [sic.] truncata – Benson et al. 1961: Q356, fig. 274.7a-c. Saida torresi – Swanson 1969: 47, Pl. 6, figs 101, 102. Saida sp. McKenzie 1974: 161, Pl. 2, fig. 2.13. Saida torresi – Whatley & Downing 1983: 363, Pl. 3, fig. 8. Saida torresi – Puri & Hulings 1976: 292, Pl. 12, figs 12, 13, Fig. 12. Saida bellsensis McKenzie, Reyment & Reyment 1991: 148, Pl. 3, fig. 12, Pl. 4, fig 1, Pl. 11, fig. 6. Saida daisa McKenzie, Reyment & Reyment 1993: 86, Pl. 2, figs 9-10. Saida torresi – Yassini & Jones 1995: 350, Figs 361, 363. Saida torresi – Wouters 2007: 132.

Description. A relatively large Saida, sub-ovo/rectangular in lateral view with straight dorsal margin, curved anterior and posterior margins, and slightly inflexed ventral margin. The ventral ala is evenly curved, convex in section, and terminates at mid-height. The postero- dorsal ridge is evenly curved and about two-fifths of the total length. The macro-reticulation defines much of the surface ornament, with a finer network of secondary reticulation between the primary anterior and posterior reticulation resulting in finer punctae in those areas. The dominant murae across the lateral surface often extend in a continuous line to the pronounced marginal denticulation. For much of the valve circumference, the inner limits of the marginal rim are defined by a sharp ridge.

Remarks. Though Saida daisa McKenzie, Reyment & Reyment (1993) is considerably smaller than Saida sp. aff. S. daisa, they share the inflated, convex alar. The short, rounded spine described as occurring behind maximum alar height for Saida daisa could not be seen in the illustrations (McKenzie, Reyment & Reyment 1993) nor observed on these specimens, and the postero-dorsal ridge in Saida sp. aff. S. daisa is shorter than that of Saida daisa. Ayress (1995) treated the southern Victorian Late Eocene Saida daisa McKenzie, Reyment &

165

Plate 3.

A-C. Oculocytheropteron microfornix Whatley & Downing, 1983. A. CRV. B. dorsal. C. CRV. D. Cytheropteron sp. aff. C. ruwarungensis Majoran, 1997, CRV. E-F. Oculocytheropteron ayressi varius subsp. nov. E. CLV. F. C dorsal. G-J. Aversovalva yarringa yarringa McKenzie, Reyment & Reyment, 1993. G-H. CRV. I. C dorsal. J. CLV. K. Pseudeucythere? sp. CRV. L. Indet. gen. sp. 2 CLV. M. Pseudeucythere pseudosubovalis (Whatley & Downing, 1983), CLV. N. Indet. gen. sp. 1 CRV. O. Ruggieriella sp. CLV. P. Orlovibairdia sp. CRV. Q. Uroleberis minutissima (Chapman, Crespin & Keeble, 1926), CRV.

Scale bar = 100 µ, D, E, F, P, Q. Scale bar = 50 µ, A, B, C, G, H, I, J, K, L, M, N, O.

166

Reyment (1993) as synonymous with S. limbata Colalongo & Pasini (1980) from Calabrian Plio-Pleistocene but, based on comparison of ornament, this does not seem likely. Saida bellsensis McKenzie, Reyment & Reyment (1991) is also very similar to Saida sp. aff. S. daisa but the latter is larger, the postero-dorsal ridge more pronounced, and the straight portion of the dorsum longer, resulting in a shorter, steeper antero-dorsal outline.

Cythere torresi Brady (1880), described from Recent dredged sediments from Torres Strait, is 0.38 mm in length. Hornibrook erected the mono-specific genus Saida with S. truncala Hornibrook (1952) as type species, but later, having examined Cythere torresi (Brady 1880), he thought Brady's to be the senior synonym (Swanson 1969). This assumption is questioned by Wouters (2007); he suggests that despite the differences between Saida species being very small, S. truncala Hornibrook (1952) and Cythere torresi Brady (1880) may not be synonymous. Swanson (1969) identified a Saida species as S. torresi in one Early Miocene New Zealand assemblage. When his illustration, Hornibrook's Saida truncala, and Puri & Hulings' (1976) optical photographs of the external view of Cythere torresi Brady (1880) lectotypes are compared, there are evident similarities of outline in lateral view, especially in the low, oblique angles of the antero- and postero-dorsal margins as they descend from the virtually straight medio-dorsal area, but whether these similarities extend to other features is difficult to ascertain using their images. The author regards the identification of specimens as Saida torresi to be currently problematic.

Whatley & Downing (1983) identified 31 Saida specimens in a Middle Miocene Victorian assemblage as Saida torresi. Saida sp. aff. S. daisa has comparable anterior, dorsal and posterior outlines, marginal rims of similar width, pattern of ornament the same, and the postero-dorsal ridge having the same shape and length. The notable differences are the more pronounced sinuosity of the former taxon's ventral margin and its smaller size. It is possible that the Whatley & Downing (1983) taxon is not Saida torresi, and that it is closely related to, or synonymous with, Saida sp. aff. S. daisa.

Ayress (1996) described Cytherura nonspinosa from Late Eocene New Zealand assemblages, he has since indicated that the species belongs in Saida (Ayress lit. comm. 2014).

Saida torresi (Yassini & Jones 1995) has a postero-dorsal ridge of similar length and curvature but theirs is thicker, broader and more rounded than Saida sp. aff. S. daisa. As the size bar is missing from their illustration, sizes cannot be compared. There is also a broader, raised mural alignment from the centre of the lateral surface to the postero-ventral angle of the ventral ala.

A particularly remarkable feature of the Australian Saida reviewed was consistency of pattern between taxa of both macro reticulation and the finer intramural reticulation found in Saida sp. (McKenzie 1974), Saida torresi Whatley & Downing (1983), Saida bellsensis McKenzie, Reyment & Reyment (1991), Saida daisa McKenzie, Reyment & Reyment (1993), and Saida torresi (in Yassini & Jones 1995).

Measurements. LV: 0.5 mm, breadth 0.29 mm. C: length 0.45 mm, height 0.31 mm, breadth 0.23 mm. C: length 0.41 mm, height 0.29 mm, breadth 0.23 mm.

Material studied. Seven specimens.

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Occurrence and age. Gellibrand Marl: Heywood-10 bore, depth 335.28 m: Globigerina euapertura foraminiferal zone (GEDIS), Late Oligocene (Chaproniere et al. 1996).

Family BYTHOCYTHERIDAE Sars, 1926 Sclerochilus Sars 1866 Sclerochilus sp. Plate 1S

Description. A smooth, elongate Sclerochilus with rounded anterior and dorsal margins, ventral margin sinuous and strongly inflexed anterior of the median. Maximum length medial, maximum height at two-thirds of length. Adductor muscle scars five in number, elongate, obliquely aligned. Anterior and posterior vestibules observed through thin carapace.

Remarks. Sclerochilus sp. McKenzie, Reyment & Reyment (1993) is only slightly larger than this specimen, but is more elongate, and the ventral margin less inflexed.

Measurements. C: length 0.46 mm, height 0.21 mm.

Material studied. One specimen.

Occurrence and age. Gellibrand Marl: Heywood-10 bore, depth 335.28 m: Globigerina euapertura foraminiferal zone (GEDIS), Late Oligocene (Chaproniere et al. 1996).

Family LOXOCONCHIDAE Sars 1925 Loxoconcha Sars 1866 Loxoconcha punctabella McKenzie, Reyment & Reyment 1991 Plate 2C-D

Loxoconcha punctabella McKenzie, Reyment & Reyment 1991: 151, Pl. 4, fig. 3, Pl. 5, figs 5, 6.

Description. A medium-sized, sub-rhomboid to sub-oval Loxoconcha with concentrically aligned punctae that are rectangular peripherally and round medially.

Remarks. Loxoconcha propunctata Hornibrook (1952) is very similar in appearance to L. punctabella but has a higher, more broadly rounded anterior margin and its caudal extension is below the midline. Loxoconcha sp. McKenzie, Reyment & Reyment (1993) has a lateral view comparable to L. punctabella but with coarser ornament.

Measurements. Length 0.45–0.54 mm, height 0.32 mm.

Material studied. Three specimens.

Occurrence and age. Gellibrand Marl: Heywood-10 bore, depth 335.28 m: Globigerina euapertura foraminiferal zone (GEDIS), Late Oligocene (Chaproniere et al. 1996).

Family XESTOLEBERIDIDAE Sars 1928 Uroleberis Triebel 1958 Uroleberis minutissima (Chapman 1926) Plate 3Q

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Bairdia minutissima Chapman 1926: 132, Pl. 10, figs 2a, b. Uroleberis sp. – Triebel 1958: 110, Pl. 3, figs 14 a, b. Uroleberis minutissima – McKenzie 1974: 163, Pl. 1, fig. 14. Uroleberis minutissima – Whatley & Downing 1983: 384, Pl. 7, fig. 20. Uroleberis minutissima – Warne 1987: 444. Foveoleberis sp. – McKenzie, Reyment & Reyment 1990: 17, Pl. 5, fig. 4, Pl. 8, fig 7. Foveoleberis minutissima – McKenzie, Reyment & Reyment 1991: 154, Pl. 5, fig. 12. Uroleberis sp. cf. minutissima – Neil 1992: 194-195, Pl. 17, fig. H. Foveoleberis minutissima sublaevis – McKenzie, Reyment & Reyment 1993: 89, Pl. 3, fig. 9. Uroleberis minutissima – Ayress 1995: 901 (Table 1), Figs 12.4-6. Uroleberis minutissima – Neil 2006: 56-57, Figs 5K, L.

Remarks. As with Neil’s (2006) Middle Miocene assemblage from the Wuk Wuk Marl, Gippsland, Victoria, these specimens display variability in the fine surface punctae. In some specimens these are uniformly distributed across the surface, others appear virtually smooth. As the carapaces are fragile, an attempt to open one to view the hinge elements was unsuccessful. For the diagnostic and taxonomic reasons discussed by McKenzie et al. (1991, 1993) and Neil (2006), the Foveoleberis genus and sublaevis subgenus have not been adopted.

Measurements. C: length 0.55 mm, height 0.38 mm, breadth 0.38 mm.

Material studied. Six carapaces.

Occurrence and age. Gellibrand Marl: Heywood-10 bore, depth 335.28 m: Globigerina euapertura foraminiferal zone (GEDIS), Late Oligocene (Chaproniere et al., 1996).

Family PECTOCYTHERIDAE Hanai 1957 Ruggieriella Colalongo & Pasini 1980 Ruggieriella sp. Plate 3O

?Phlyctobythocythere sp. 2 Whatley & Downing 1983: 365, Pl.3, fig. 13.

Remarks. Ruggieriella sp. differs from R. decemcostata Colalongo & Pasini (1980) in being smaller, the longitudinal ridges on the lateral surface are far less well defined, the anterior margin projects further forward and possesses a narrow, distinct ridge just inside the inner margin (Colalongo & Pasini (1980; Ayress lit. comm. 2014). Ruggieriella sp. is similar to ?Phlyctobythocythere sp. 2 Whatley & Downing (1983) though Ruggieriella sp. is larger and its longitudinal ridges less well defined.

Measurements. C: length 0.45 mm, height 0.25 mm.

Material studied. One carapace.

Occurrence and age. Gellibrand Marl: Heywood-10 bore, depth 335.28 m: Globigerina euapertura foraminiferal zone (GEDIS), Late Oligocene (Chaproniere et al. 1996).

Family ROCKALLIIDAE Whatley, Uffenorde, Harlow, Downing & Kesler 1982 Rockallia Whatley, Frame & Whittaker 1978 Rockallia sp. Plate 2J

169

Plate 4.

A. Bradleya (Quasibradleya) momitea McKenzie, Reyment & Reyment, 1993, CRV. B. Bradleya sp. cf. B. regularis McKenzie, Reyment & Reyment, 1991, CRV. C. Trachyleberis brevicosta major McKenzie, Reyment & Reyment, 1991, CRV. D-E. Glencoeleberis? sp. aff. G?. thomsoni. D. Surface detail. E. MLV. F. Cytheropteron sp. aff. C. ruwarungensis Majoran, 1997, C dorsal outline traced from digital optical photo, the specimen is not tilted, therefore the asymmetry is presumed to be due to deformation. G-H. Cytherelloidea marginopytta McKenzie, Reyment & Reyment, 1991. G. Detail of second, third and fourth orders of ornament. H. FCRV.

Scale bar = 100 µ, A, B, C, E, H. Scale bar = 20 µ, D, G.

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Arcacythere sp. McKenzie 1974: Pl. 4, fig. 10. Arcacythere sp. aff. chapmani Hornibrook 1952 – McKenzie, Reyment & Reyment 1991: 158, Pl. 6, fig. 5. Arcacythere aff. chapmani – McKenzie, Reyment & Reyment 1993: 93, Pl. 3, fig. 26, Pl. 8, fig. 6. Arcacythere eocenica Whatley, Uffenorde, Harlow, Downing & Kesler 1982 – Majoran 1995: Fig. 3S, Appendix table. Arcacythere eocenica – Majoran 1996b: Appendix Table 1.

Remarks. Based on the summary of criteria for distinguishing between Arcacythere and Rockallia (Mazzini 2004), this specimen and its synonyms display the features characteristic of Rockallia – a sub-rounded to bluntly acuminate posterior outline in lateral view, lack of both anterior and posterior thick marginal rims, and absence of a pronounced antero-dorsal ridge; ornament dominated by fossae rather than by murae. One criterion not observed is possession of a sub-central node. Though larger than the material used by McKenzie, Reyment & Reyment (1991, 1993), this single carapace has the same shape and distinctive pattern of fossae. Compared to the Australian examples of Arcacythere eocenic, Arcacythere cf. eocenica in Ayress (1994) has a less regular outline in lateral view with a more concave dorsal margin, a pointed rather than curved postero-dorsal angle, and has much courser fossae differently aligned to that of Arcacythere eocenic.

Arcacythere chapmani Hornibrook (1952) is retained in Arcacythere.

Measurements. C: length 0.53 mm, height 0.28 mm, breadth, 0.26 mm.

Material studied. Sing le carapace.

Occurrence and age. Gellibrand Marl: Heywood-10 bore, depth 335.28 m: Globigerina euapertura foraminiferal zone (GEDIS), Late Oligocene (Chaproniere et al. 1996).

Family CYTHERURIDAE Müller 1894 Subfamily CYTHEROPTERONINAE Hanai 1957 Cytheropteron Sars 1866 Cytheropteron sp. aff. C. ruwarungensis Majoran 1997 Plate 3D

Cytheropteron ruwarungensis Majoran, 1997: 428, Fig. 6.1-4.

Description. A medium-sized cytheropterine ostracod with an ovate dorsal view (due to the narrow, in-curving alae) interrupted only by the blunt anterior and short, keel-like caudal process. Alae lack terminal apical spine. Characteristic is a reticulate pattern of low, widely spaced ridges; the entire external surface is covered with micropunctae, and there is a large, deep mid-ala depression. The valves are sub-equal, right valve overlapping left.

Remarks. This taxon is closely related to Cytheropteron ruwarungensis Majoran (1997), but the reticulation – so evident on Cytheropteron sp. aff. C. ruwarungensis – is barely discernable in the illustrations of C. ruwarungensis and does not appear to always conform with that of this specimen. Cytheropteron acutangulum Hornibrook (1952) has a similar ovate dorsal view, but is smaller, and lacks the mid-ala depression.

Measurements. C: length 0.51 mm, height 0.3 mm, width 0.33 mm.

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Material studied. Single carapace.

Occurrence and age. Gellibrand Marl: Heywood-10 bore, depth 335.28 m: Globigerina euapertura foraminiferal zone (GEDIS), Late Oligocene (Chaproniere et al. 1996).

Family TRACHYLEBERIDIDAE Sylvester-Bradley 1948 Subfamily TRACHYLEBERIDINAE Sylvester-Bradley 1948 Acanthocythereis Howe 1963 Acanthocythereis sp.

Acanthocythereis sp. McKenzie, Reyment & Reyment 1993: 106, Pl. 6, fig. 10.

Remarks. This anterior portion of an adult right valve is morphologically close to Acanthocythereis sp. McKenzie, Reyment & Reyment (1993) from the Middle(?) Eocene of Browns Creek.

Material studied. One adult right valve fragment.

Occurrence and age. Gellibrand Marl: Heywood-10 bore, depth 335.28 m: Globigerina euapertura foraminiferal zone (GEDIS), Late Oligocene (Chaproniere et al. 1996).

Family THAEROCYTHERIDAE Hazel 1967 Subfamily BRADLEYINAE Benson 1972 Bradleya Hornibrook 1952 Bradleya sp. cf. B. regularis McKenzie, Reyment & Reyment 1991 Plate 4B

Bradleya sp. cf. regularis McKenzie, Reyment & Reyment 1991: 164, Pl. 6, fig. 13.

Affinity Bradleya regularis McKenzie, Reyment & Reyment 1991: 164, 166, Pl. 6, figs 11-12.

Description. A moderate-sized, inflated Bradleya, sub-rectangular in lateral view with surface covered by reticulate ornament; ventral ridge alate, extending from antero-ventral to postero- ventral area; a less pronounced dorsal ridge curves evenly from below the semi-spherical eye tubercle to the postero-dorsal angle. Medial longitudinal murae are roughly aligned before and behind the subcentral tubercle. Median ridge, characteristic for the subgenus Quasibradleya, is lacking. Anterior margin convex, dorsum inflexed, posterior dentate and convex, ventrum straight to convex. Outline hastate in dorsal view; anterior margin blunt, projecting forward only minimally. CMS with two adductor scars.

Remarks. The convex posterior margin and ornament of the single carapace matches Bradleya sp. cf. regularis McKenzie, Reyment & Reyment (1991). The specimen is similar in size to Bradleya regularis McKenzie, Reyment & Reyment (1991) but Bradleya sp. cf. B. regularis is less elongate and the posterior margin convex not concave above the caudal process.

Measurements. C: length 0.81 mm, height 0.46 mm, breadth 0.5 mm.

Material studied. Two specimens, one an adult carapace, the other a broken RV.

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Occurrence and age. Gellibrand Marl: Heywood-10 bore, depth 335.28 m: Globigerina euapertura foraminiferal zone (GEDIS), Late Oligocene (Chaproniere et al. 1996).

Family INCERTAE SEDIS Indet. sp. 1 Plate 3N

Description. A small, smooth, sub-ovate ostracod. In lateral view, the anterior, ventral and posterior margins are convex; the dorsal margin is highest antero-dorsally. There is a thin, narrow keel extending from one-third of the length to the posterior and parallel to the ventral margin. No internal details are visible. As the valves are damaged and slightly displaced relative to each other, the valve overlaps are not clear. Although this specimen and Indet. sp. 2 may well both be cytherellids, there are neither platycopid or podocopid diagnostic features visible, hence the rationale for incertae sedis.

Measurements. C: length 0.35 mm, height 0.24 mm.

Material studied. One damaged carapace.

Occurrence and age. Gellibrand Marl: Heywood-10 bore, depth 335.28 m: Globigerina euapertura foraminiferal zone (GEDIS), Late Oligocene (Chaproniere et al. 1996).

Indet. sp. 2 Plate 3L

Description. A small, smooth, moderately thick-shelled, sub-rounded ostracod; anterior, posterior and ventral margins convex; dorsal margin highest antero-dorsally then slightly inflexed before descending convexly to the posterior. Maximum length approximately medial; maximum breadth two-thirds of the length and below the median. There is a narrow keel parallel and adjacent to the ventral margin. Normal pores scattered across the valve surfaces. Left valve overlaps right. No CMS or other diagnostic features observed.

Measurements. C: length 0.32 mm, height 0.24 mm, breadth 0.18 mm.

Material studied. One carapace.

Occurrence and age. Gellibrand Marl: Heywood-10 bore, depth 335.28 m: Globigerina euapertura foraminiferal zone (GEDIS), Late Oligocene (Chaproniere et al. 1996).

CONCLUSION

The subsurface Gellibrand Marl sample yielded 409 specimens across 53 taxa. It was both larger, and had a higher level of diversity than the older Narrawaturk Formation assemblage from the same location (Section 6 herein), and greater diversity than the South Australian Early Oligocene Port Willunga Formation/Ruwarung Member assemblage. Although there are indications of at least part of the assemblage being allochthonous, there are no cold or deep- water taxa. The depositional environment of the assemblage was offshore, still reasonably shallow, warm, and with a well-oxygenated benthos. It was somewhat deeper and further from shore than for the Early Oligocene Narrawaturk Formation at this location, indicative of a more transgressive phase.

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It is beyond the scope of this study to incorporate the six upsection ostracod assemblages from Heywood-10 (Table 1). All are Miocene, four are from the Gellibrand Marl and two are from the Port Campbell limestone, none have so far been described but they have the potential to provide further data for palaeoenvironmental interpretation at this site.

ACKNOWLEDGEMENTS

Grateful thanks for extensive supervisory guidance, support and editorial comment are extended to Kelsie Dadd, John A. Talent and Ruth Mawson of Earth and Planetary Sciences, Macquarie University. The comments and recommendations of the referees Michael Ayress, Alan Lord and Mark Warne are deeply appreciated and grateful thanks extended.

REFERENCES

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MCKENZIE, K. G., 1979. Appendix 2. Notes on Ostracoda from Willunga Embayment boreholes WLG38, WLG40 and WLG42. In Eocene to Miocene Stratigraphy of the Willunga Embayment, B. J. Cooper, Geological Survey of South Australia, Reports of Investigations No. 50, 90-101. MCKENZIE, K. G., 1979. Tasmanocypris, a new marine ostracode genus, and a review of the family Paracyprididae (Crustacea; Ostracoda). Papers and Proceedings of the Royal Society of Tasmania 113, 29-37. MCKENZIE, K. G. & GUHA, D. K., 1987. A comparative analysis of Eocene/Oligocene boundary Ostracoda from southeastern Australia and India with respect to their usefulness as indicators of petroleum potential. Transactions of the Royal Society of South Australia 111(1), 15-23. MCKENZIE, K. G., REYMENT, R. A. & REYMENT, E. R., 1991. Eocene-Oligocene Ostracoda from South Australia and Victoria, Australia. Revista Española de Paleontologia 6(2), 135-175. MCKENZIE, K. G., REYMENT, R. A. & REYMENT, E. R., 1993. Eocene Ostracoda from the Browns Creek Clays at Browns Creek and Castle Cove, Victoria, Australia. Revista Española de Paleontologia 8(1), 75-116. MCKENZIE, K. G. & WARNE, M. T., 1986. Alataleberis new genus (Crustacea, Ostracoda) from the Tertiary of Victoria and South Australia. Proceedings of the Royal Society of Victoria 98(1), 31-40. NEALE, J. W., 1975. The ostracod fauna from the Santonian Chalk (Upper Cretaceous) of Gingin, Western Australia. Special Papers in Palaeontology 16, The Palaeontological Association, London, 1-81, 22 plates. NEIL, J. V., 1995. Palaeobiogeography of some Oligocene-Miocene ostracode assemblages from southeastern Australia. In Ostracoda and Biostratigraphy - Proceedings of the 12th. International Symposium on Ostracoda, Prague, 1994. A. A. Balkema, Rotterdam, 215-224. NEIL, J. V., 2006. Taxonomy of an ostracode assemblage from the Middle Miocene Wuk Wuk Marl, Gippsland, Victoria. Proceedings of the Royal Society of Victoria 118(1), 35-63. NOHARA, T. & YABU, S., 1983. Notes on Ostracode genus Saida from the Ryukyus. Bulletin of the College of Education, University of the Ryukyus 26, 65-71. PURI, H. S. & HULINGS, N. C., 1976. Designation of lectotypes of some ostracods from the Challenger expedition. Bulletin of the British Museum (Natural History Zoology) 29(5), 249-315, 27 pls, 14 text figs. SWANSON, K. M., 1969. Some Lower Miocene Ostracoda from the middle Waipara district, New Zealand. Transactions of the Royal Society of New Zealand 7(3), 33-48. TAYLOR, D. J., 1964a. Biostratigraphy Heywood No. 10 bore section. Geological Survey of Victoria, Unpublished Report, 26/10/64, Department of Manufacturing and Industry Development, Melbourne, 1-4. TAYLOR, D. J., 1964b. Biostratigraphic log Heywood No. 10 bore. Geological Survey of Victoria, Unpublished Report 24.11.64, Department of Manufacturing and Industry Development, Melbourne, 1. TAYLOR, D. J., 1971 Chapter 10 – Foraminifera and the Cretaceous and Tertiary depositional history. In The Otway Basin of Southeastern Australia, H. Wopfner & J. G. Douglas, eds, Special Bulletin, Geological Surveys of South Australia and Victoria, 217-234, enclosures 10.1 and 10.2. WARNE, M. T., 1987. Lithostratigraphical associations of the ostracode fauna in the marine Neogene of the Port Phillip and Western Port Basins, Victoria. In Shallow Tethys 2, The

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SECTION 8

GLENCOELEBERIS? THOMSONI (CRUSTACEA: OSTRACODA) AS EVIDENCE FOR A LATEST PALEOCENE/EARLIEST EOCENE MARINE PASSAGE BETWEEN THE AUSTRALO-ANTARCTIC GULF AND THE TASMAN SEA

COL EGLINGTON

Department of Earth and Planetary Sciences, Macquarie University, Sydney, NSW 2109, Australia. [email protected]

EGLINGTON, C. Glencoeleberis? thomsoni (Crustacea: Ostracoda) as evidence for a latest Paleocene/earliest Eocene marine passage between the Australo-Antarctic Gulf and the Tasman Sea.

Key words. Paleocene, Ostracoda, Wangerrip Group, Dilwyn Formation, Rivernook, Latrobe-1, Otway Basin, Australia, Australo-Antarctic Gulf, Tasman Sea.

ABSTRACT

Glencoeleberis? thomsoni Hornibrook (1952), found in and above the latest Paleocene/earliest Eocene Pember Mudstone Member, in Early Eocene Rivernook Member, and in Late Paleocene/Early Eocene dredged marine sediments from Fiordland in the South Island, New Zealand, provides evidence for an early breach of the Tasmanian land-bridge connecting Australia and Antarctica. Previous work suggested that breaching of the land bridge closing the eastern end of the Australo-Antarctic Gulf (that had prevented through-flow into the Tasman Sea) commenced in the mid-Late Eocene. The extension in distribution of this otherwise exclusively regional species to both sides of the Tasmanian block is evidence for a latest Paleocene/earliest Eocene breach of the barrier allowing migration from the Australo- Antarctic Gulf into the Tasman Sea. Glencoeleberis? thomsoni Hornibrook (1952), incidentally, has diagnostic features of Actinocythereis, Glencoeleberis and Trachyleberis. Its generic location is questioned because of the alignment of tubercles, the ribs beneath the rows of tubercles are sometimes very minimal, and there is thickening of the marginal pore canals. Glencoeleberis? thomsoni is morphologically diverse, including a dwarf form; both large and dwarf forms are present in Australian and New Zealand assemblages.

INTRODUCTION

Research projects over the past two decades centred on the Deep Sea Drilling Program (DSDP), Ocean Drilling Program (ODP) and the Integrated Ocean Drilling Program (IODP), have enabled considerable headway to be made interpreting Earth history, including events related to the Southern Hemisphere Gondwana breakup, and development of the AAG and the Tasman Sea. The breakup of Gondwana was well underway by the end of the Paleocene with the separating Antarctic and Australian blocks creating the Australo-Antarctic Gulf (AAG) (Fig. 1) (Duddy 2003; Cande & Stock 2004). In the Paleocene, this gulf was an almost completely enclosed, deep marine basin with extensive shallow continental shelves, open at the western end to the inflow of warm surface waters from the Indian Ocean (Exon et al. 2004d). The eastern end was part of a broad, shallow, continental shelf with restricted circulation in some parts, and particularly poor ventilation. A west-east current is assumed to have flowed along the northern region, part of a weak, clockwise gyre (Exon et al. 2004d).

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Fig. 1. Tectonic and oceanographic reconstructions of the Australo-Antarctic Gulf (AAG) and Tasman Sea regions, Early Eocene, arrows indicate the main current flow (adapted from McGowran et al. 1997b; Cande & Stock 2004; Exon, Kennett & Malone 2004d). STS = South Tasman Saddle, OB = Otway Basin, FA = Fiordland area.

Correlation, dating, and palaeoenvironmental interpretation of strata has relied overwhelmingly on micropalaeontological studies, utilising foraminiferans, nannofossils, dinoflagellates, diatoms and spores/pollens, in particular the work of Carter (1958a, 1958b, 1964), Dettman & Playford (1969), McGowran (1969, 1970, 1971, 1978, 1979, 1986, 1989, 1991), Harris (1971), Ludbrook (1971), McGowran et al. (1971, 1992, 1997, 2000, 2004),

Taylor (1971a, 1971b), Stover & Partridge (1973), Stover & Evans (1974), McGowran & Beecroft (1986a, 1986b) and McGowran & Li (1996, 2000, 2007). When available, ostracods, as predominantly marine, benthic, calcitic crustaceans, have also provided valuable palaeoenvironmental and palaeogeographic information (McKenzie 1973, 1974, 1978; McKenzie & Peypouquet 1984; McKenzie et al. 1990, 1991, 1993; Ayress 1993a, 1993b, 1993c, 1994, 1995; Warne 1993, 2000, 2002, 2005; Neil 1994, 1995, 1997; Warne & Idris 1995; Majoran 1995, 1996a, 1996b, 1997; Szczechura & Błaszyk 1996; and Szczechura 2001).

Initially, the Tasmanian land bridge connecting the Australian and Antarctic plates prevented marine migration between the Tasman Sea and the AAG. Based primarily on sedimentary evidence from ODP and IODP, this barrier is estimated to have been significantly breached in the latest Eocene–earliest Oligocene (~33.5–33.9 Ma), but with some deepening of the Tasmanian Gateway earlier ~35.5 Ma, in the middle Late Eocene (Exon et al. 2001; Brinkhuis et al. 2003a, 2003b; Sluijs et al. 2003; Cande & Stock 2004; Exon et al. 2004a, 2004b, 2004d). This deep opening then allowed the strong through-flow that became a major contributor to the development of the Antarctic Circumpolar Current (Exon et al. 2004d).

McNamara (2000), Lawver & Gahagan 2003 and Exon et al. (2004d) suggested there was an earlier, very shallow marine linkup through the South Tasman Saddle. The earliest inferred date for such a passage is Paleocene (Exon et al. 2004d), but Lawver & Gahagan (2003) assert that East Antarctica would have blocked any possible breach through the western end of the South Tasman Saddle (Fig. 1) prior to the Eocene. Structurally, a breach is possible as Exon et al. (2004d) describe how Cretaceous rifting caused crustal thinning resulting in subsidence of parts of the Tasmanian region to near sea level allowing very limited interchange of shallow-marine waters between the AAG and Pacific Ocean. Exon et al.

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(2004d) base the existence of this breach on a regional erosional unconformity and dinocyst distribution patterns in cores from IODP along the Wilkes Land coastal margin and ODP in the Tasmanian Gateway.

A trachyleberid, Glencoeleberis? thomsoni Hornibrook (1952), found in South Australian (Majoran 1995, 1996a, 1996b), Victorian Otway Basin (Eglington 2006; Sections 2 and 3 herein), and New Zealand assemblages (Hornibrook 1952; Milhau 1993; Ayress 1993a, 1993b, 1995, 2006) is evidence for a possible marine connection between the Tasman Sea and AAG by latest Paleocene/earliest Eocene.

LOCATIONS, STRATIGRAPHY AND AGES

Ostracod assemblages are present in bores and outcrop in southeastern Australia including the Latrobe-1, Heywood-10 and Narrawaturk-2 bore cores, Rivernook Member outcrop, and Castle Cove and Browns Creek sections. Samples were treated with hydrogen peroxide, washed, sieved and picked using standard methods.

Fig. 2. Locations and structures within the Otway Basin, Victoria, Australia (after Wopfner & Douglas 1971).

In the Latrobe-1 bore (Figs 2 and 3) the latest Paleocene/earliest Eocene Pember Mudstone Member of the Dilwyn Formation, Wangerrip Group, is the lowermost unit containing ostracods. Near the base of the Pember Mudstone are two thin subunits, the Rivernook Member and Rivernook A Bed. The bore intercepts three additional Dilwyn subunits of relevance, these are the Princetown, Trochocyathus and Turritella beds. The Rivernook Member outcrops in a coastal exposure between Point Ronald and Moonlight Head (Fig. 3), where it consists of 6 m of glauconitic and limonitic sandstone and claystone. A lower unit of similar lithology, the Rivernook A Bed, is usually concealed by beach sand (McGowran 1970; Abele et al. 1993). The Princetown, Rivernook and Rivernook A strata are interpreted as ingressions, with each subunit containing its own distinctive foraminiferal assemblage (McGowran 1965, 1970, 1991; Taylor 1964a, 1965, 1971). The Rivernook A and Rivernook marine ingressions are considered to be Chron 24; Rivernook A is dated as earliest Early Eocene (Ypresian), planktonic foraminiferal zone P6a; and the Rivernook Ingression as Early Eocene (Ypresian), upper Chron 24, P6b zone (McGowran et al. 2000).

Browns Creek and Castle Cove are located in the Aire district of southwestern Victoria (Figs 2 and 4). The main exposures of the Browns Creek Clays are in two coastal gullies approximately midway between Rotten Point and the mouth of the Johanna River (Fig. 3) where up to 43 m of Late Eocene (P15-P17) marine sandy and marly mudstone is exposed

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Fig. 3. Latrobe-1 and Rivernook locations, Otway Basin, southern Victoria (Eglington 2006).

(Carter 1958a; Abele et al. 1976; McKenzie et al. 1993; Chaproniere et al. 1996; Holdgate & Gallagher 2003). Castle Cove (Fig. 3) has the most continuous Cenozoic sections in the region (Table 1), including a short, exposed sequence of Johanna River Sands (Middle Eocene) that overlie Mesozoic sandstone and are overlain by 25 m of Late Eocene Browns Creek Clays. A 15 m sand-covered interval separates the two Eocene units. This is transitionally overlain by 26 m of very Late Eocene/very Early Oligocene Castle Cove Limestone (Carter 1958; Abele et al. 1976; McKenzie et al. 1993; Holdgate & Gallagher 2003).

Fig. 4. Browns Creek and Castle Cove locations, Otway Basin, southern Victoria (modified from McKenzie et al. 1993).

Age Formation Unit

Early Miocene Gellibrand Marl Upper Glen Aire Clays

L. Oligocene/E. Miocene Gellibrand Marl Calder River Limestone

Early Oligocene Narrawaturk Fm Lower Glen Aire Clays

L. Eocene/E. Oligocene Narrawaturk/Mepunga Fms Castle Cove Limestone

Late Eocene Mepunga Formation Browns Creek Clays

Late Eocene Dilwyn Formation Johanna Sands

Table 1. Castle Cove stratigraphy (after Holdgate & Gallagher 2003).

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Unit Location Age Author

Australia Pebble Point Formation Pebble Point, Otway Late Paleocene Neil 1997 Basin, southwestern Victoria Blanche Point and Port South Australia Late Eocene and Majoran 1995, Willunga Formations Eocene/Oligocene 1996a, 1996b boundary

New Zealand Dredged marine Off the Fiordland coast, Waipawan Stage Hornibrook sediments southeastern South Island (latest Paleocene/Early 1952 Eocene, 55.8-53.3 Ma) Waikari Middle Wiapara district, Early Miocene Swanson 1969 Formation/Pareora Canterbury Province, west Series coast of South Island Warkworth and Kawau Waitemata Basin, North Early Miocene Milhau 1993 Subgroups Island Kokoamu Greensand North Otago and South Late Oligocene to Ayress 1993a, and Otekaike Canterbury, north coast of Early Miocene 2006 Limestone North Island Hampden Formation Hampden, southwest coast Middle Eocene Ayress 1993b of South Island Ashley Formation Waihao district, southern Late Eocene Ayress 1995 Canterbury Province, west coast of South Island

Table 2. Australian and New Zealand locations or strata referred to from published papers.

The Narrawaturk-2 bore is located on the coast, approximately 42 km southeast of the Warrnambool township and 25 km northwest of Latrobe-1 bore (Fig. 2). The Narrawaturk-2 bore is east of the Heywood-10 bore (Fig. 2) and intercepts the same sedimentary sequences. Other Australian and New Zealand locations or strata referred to from published papers are listed in Table 2.

RESULTS AND DISCUSSION

Evidence for an early marine route between the Australo-Antarctic Gulf (AAG) and the Tasman Sea

Latest Paleocene/earliest Eocene. The earliest evidence of an exclusively regional ostracod species inhabiting both sides of the Tasmanian block is Glencoeleberis? thomsoni Hornibrook (1952). This species is present in the Pember Mudstone Member, of Latest Paleocene/earliest Eocene age, below the earliest Eocene Rivernook A Bed. Glencoeleberis? thomsoni is also in and above the Early Eocene Rivernook Member (Eglington 2006; Sections 2 and 3 herein), as well as in dredged marine sediments dated as Waipawan (local New Zealand stage approximately Late Paleocene/Early Eocene ~52 to ~56.5 Ma) from the Fiordland area, South Island of New Zealand (Hornibrook 1952). The possibilities are that:

1. Glencoeleberis? thomsoni was initially present in the AAG during the earlier Paleocene (but due to dearth of Paleocene strata in southern Australia, has not previously been observed from older strata), that it migrated with the AAG current and accessed the Tasman Sea by the latest Paleocene/very early Early Eocene via a shallow (transient) marine route through the area south of Tasmania to colonise New

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Zealand by the Waipawan. Exon (personal communication in Lawver & Gahagan 2003) expressed the possibility that a marine connection through the Tasman Saddle (Fig. 1) may have existed before the Eocene but Lawver & Gahagan (2003) revised this date upwards to earliest Eocene, contending that East Antarctica would have blocked that region until earliest Eocene. Such a passageway would have been very shallow, low energy, ephemeral or episodic, and have had little or no affect on the prevailing currents in the AAG or the Tasman Sea.

2. Glencoeleberis? thomsoni was endemic to New Zealand, migrated across the Tasman Sea and Tasmanian area by the end of the Paleocene/earliest Eocene, travelled against the west-to-east current along the southern Australian coast that is part of the AAG’s clockwise gyre (Shafik 1990; Exon et al. 2000; Lawver & Gahagan 2003; Exon et al. 2004d; Huber et al. 2004) to southern Victoria by earliest Early Eocene (Rivernook ingression). The lack of evidence for westward ostracod migration does not support the hypothesis of a New Zealand origin. Against this scenario is the high degree of endemism in the Australian populations, evidence of Paleogene west-east migration for several different animal groups (Ayress 1995; Maxwell & Darragh 2000; McNamara 2000; Warne 2000), the weight of evidence for the New Zealand Paleogene populations to have been immigrant (Ayress 1995; Hornibrook 1952) and the endemism of long-ranging ostracod genera such as Philoneptunus and the Cytheropteron testudo/wellmani groups in New Zealand that do not occur in Australian waters (lit. comm. Ayress 2014). The difficulty for a non-swimming benthic dweller to migrate against flow has also to be considered, though it is noted that currents within the AAG were presumed to have been weak (Exon et al. 2004d).

3. Glencoeleberis? thomsoni migrated independently from a common external source to both areas, or travelled from AAG to Tasman Sea (or vice versa) via another route. So far there is no evidence of the species outside of the AAG, and Tasman Sea areas and no viable route with supporting evidence to illustrate such a path.

Glencoeleberis? thomsoni has also been recorded from South Australian and Victorian Late Eocene, (Majoran 1995, 1996a, 1996b) and New Zealand (Ayress 1995, 2006) strata, but not from outside southern Australia or New Zealand. The species displays several varieties and subspecies (Plate 1) (Ayress 1993a, 1993b; Milhau 1993; Ayress 1995; Majoran 1995, 1996a, 1996b; Eglington 2006; Sections 2 and 3 herein) as a result of early migration followed by a degree of local specialisation departing from its (also present) ancestral form. The two forms of Glencoeleberis? thomsoni, the small or "dwarf" form, and the larger form are found in assemblages from both Australia and New Zealand (Ayress 1993, 1995b, 2006); Eglington 2006; Sections 2 and 3 herein).

Early Eocene. The existence of a marine connection by the Early Eocene is supported by the presence of another invertebrate group – New Zealand Early Eocene molluscs closely related to taxa from the Victorian Late Paleocene and Early Eocene (Maxwell & Darragh 2000).

Middle Eocene. The ostracod genus Cytheralison (Hornibrook 1952) first occurs in the Upper Cretaceous Toolonga Calcilutite and Korojon Calcarenite, Carnarvon Basin, Western Australia (Bate 1972). Its oldest AAG occurrence is Early Eocene from the Turritella bed, Latrobe-1 (Eglington 2006; Sections 2 and 3 herein) and, by Middle Eocene is present in the Fiordland area of New Zealand (Fig. 1) (Hornibrook 1952). Cytheralison would appear to be unique to this Australian/New Zealand region, so its first appearance in New Zealand in the Middle Eocene (Hornibrook 1952) implies prior migration from the AAG.

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Late Eocene. By Late Eocene the faunal affinity between the two regions is even more evident. On comparing the 18 genera of the Rivernook stratum (earliest Eocene) to a list of Late Eocene New Zealand ostracods (Ayress 1995), 10 are now common to both, a further three tentatively identified in the Rivernook Member and two others are found in Latrobe-1 above the Rivernook Member and are Early Eocene. At species level, four of the New Zealand taxa are conspecific with, or closely related to Rivernook taxa, and are regional in nature (Eglington 2006; Sections 2 and 3 herein).

When Late Eocene ostracod assemblages of approximately contemporaneous age from New Zealand and southern Australia are compared, the level of conformity is very high, 56 of 61 New Zealand outer shelf or upper slope genera are also represented in southern Victorian Otway Basin sequences (Ayress 1995) indicating that a considerable number of taxa had, by this time, breached the gap. There is supporting evidence of this from New Zealand and Australian molluscan taxa (Maxwell & Darragh 2000). By contrast, the level of conformity is low between an Eocene Seymour Island Antarctic Peninsula ostracod assemblage (Szczechura 2001) and the Rivernook Member with only two, Kuiperiana and Munseyella, of the 15 Antarctic genera present.

The pattern of west-east migration from Australia to New Zealand has been documented for other taxa (Ayress 1995; McNamara 2000; Warne 2000), and would seem to be the most feasible direction for these early migrations. Evidence strongly supports the proposition that the AAG was a major passageway for the New Zealand faunas. The presence of regionally restricted taxa on both sides of the Tasmanian block is almost impossible to explain given the absence of other plausible routes between the two areas. This link dates back to the latest Paleocene/earliest Eocene, with evidence also from the Early, Middle and Late Eocene for a connection, and was certainly in place before the Eocene/Oligocene boundary.

TAXONOMY

Order PODOCOPIDA Mȕller 1894 Suborder PODOCOPA Sars 1866 Family TRACHYLEBERIDIDAE Sylvester-Bradley 1948 Subfamily TRACHYLEBERIDINAE Sylvester-Bradley 1948

Puri (1953) outlined historic problems associated with the genus Trachyleberis that had resulted in uncertainty and confusion over the diagnostic features. As an attempt to remedy this situation, he erected the genus Actinocythereis. The genus was to accommodate trachyleberidids that were closely related to Trachyleberis, but possessed spines aligned laterally in three distinct longitudinal rows, and to differentiate these species from trachyleberidids with either non-aligned, or more uniformly arranged, spines or tubercles. Another diagnostic feature of the new genus was the presence of "many paired marginal pore canals (MPC) which are generally straight, sometimes . . . wavy, but never thickened" compared to MPCs for Trachyleberis as being "numerous, wavy and thickened in the middle" (Puri 1953).

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Van Morkhoven (1963) positioned Actinocythereis as a subgenus of Trachyleberis, the only difference being "the tubercles in the posterior half of the valves arranged in three more or less distinct longitudinal rows". Hazel (1967) reviewed Actinocythereis, expanded the diagnosis, and drew on North American and Caribbean species as examples of a gradation from strongly- to weakly-aligned spines within the genus.

Warne & Whatley (1996) discussed both Actinocythereis and Trachyleberis, making the point that "all Trachyleberis species lack lateral spinose ridges" and that this "absence of raised ribs . . . . distinguishes Trachyleberis from Actinocythereis". They reassigned trachyleberidid species tetrica (Brady 1880) from Trachyleberis to Actinocythereis on the grounds that "some of the lateral surface spines are aligned along slightly raised longitudinal ribs" but that "these ribs are not very prominent" (Plate 1S, W). They also commented that "the differential diagnosis between Trachyleberis and Actinocythereis is based on character associations that are possibly a less than exact reflection of phylogenetic groupings of species within these genera".

The alignment of spines on Trachyleberis thomsoni Hornibrook (1952) has called into question its generic position. Ayress alternated between Actinocythereis (Ayress 1993b) and Trachyleberis (Ayress 1993a, 1995), and Milhau (1993) opted for Trachyleberis? due to a discernable alignment of the tubercles approaching that of Actinocythereis. Warne & Whatley (1996) retained Trachyleberis? thomsoni Hornibrook as originally designated but acknowledged the likelihood of a close relationship with Indo/Pacific species such as Actinocythereis rugibrevis (Hornibrook 1952, previously T. rugibrevis).

?Actinocythereis sp. A Neil (1994) has spinose alignment similar to that of Trachyleberis? thomsoni but if the requirement for the spines to be on ridges (Warne & Whatley 1996) is applied, it precludes this taxon as there are no discernable ridges beneath the rows of spines.

The comprehensive reassessment of the Trachyleberis genus by Brandão et al. (2013) retained only 17 species (pending review of the many hundreds of taxa previously regarded as Trachyleberis), they specifically excluded Trachyleberis thomsoni Hornibrook (1952) based on the following carapace features: lack of ocular ridge, relatively few spines on the lateral surfaces, possession of the distinct ventro-lateral ridge and showing the antero-ventral cluster of four spines (Brandão et al. 2013). To this list may be added the possession of distinct antero- and postero-marginal rims in Trachyleberis thomsoni.

In an attempt to resolve the well-documented problems of misidentifications and lost type specimens, Jellinek & Swanson (2003) reviewed the genus Trachyleberis, designated the type species and assigned lectotypes, unfortunately errors in their identifications and procedures of nomenclature have been noted and the process regarded as invalid (Warne 2008; Brandão et al. 2013). As part of their review Jellinek & Swanson (2003) erected five new trachyleberid genera, one of which is Glencoeleberis. The diagnosis for Glencoeleberis Jellinek & Swanson (2003) included: an elongate, sub-triangular outline in lateral view, spinose anterior and posterior margins, a faint ventral rib and several lateral nodes, well developed subcentral tubercle, eye tubercle present and a faint, irregular secondary reticulate ornament (Jellinek & Swanson 2003). Jellinek & Swanson (2003) tentatively assigned Trachyleberis thomsoni Hornibrook (1952) to Glencoeleberis, Ayress (2006) was similarly cautious. Brandão et al. (2013) did not refer to this new genus but did exclude T. thomsoni Hornibrook (1952) from Trachyleberis. Difficulties accommodating the various thomsoni taxa within Glencoeleberis are discussed below.

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Genus Glencoeleberis Jellinek & Swanson 2003 Glencoeleberis? thomsoni (Hornibrook 1952) Plate 1 G, Q, U non Cythere scutigera Brady – Chapman 1926: 103, Pl. 22, fig. 1. Trachyleberis thomsoni Hornibrook 1952: 33, Pl. 3, figs 40, 41, 47. Trachyleberis (Trachyleberis) thomsoni – Van Morkhoven 1963: 177. Trachyleberis thomsoni – Hazel 1967: 31. Trachyleberis thomsoni – Swanson 1969: 43, Pl. 4, figs 51-53. Trachyleberis thomsoni – Ayress 1993a: 131, 133, 137, Text Figs 3-7, Pl. 9, Q, Appendices 1-3. Actinocythereis aff. thomsoni – Ayress 1993b: Figs 3 O-P, Text Fig. 5, Table 1. Trachyleberis? thomsoni thomsoni – Milhau 1993: 192, Fig. 15. Trachyleberis thomsoni – Ayress 1995: Tables 1,3, Figs 11/4-5. Trachyleberis thomsoni – Majoran 1995: 78, 79, 80 Fig. 3G. Trachyleberis thomsoni – Majoran 1996a: Fig. 9L, Tables 1, 2. Trachyleberis thomsoni – Majoran 1996b: 20, 21, 22, 24, 27, Pl. 1 fig. 13, Tables 1, 2, Appendices 1, 2. Trachyleberis thomsoni – Warne & Whatley: 167. Glencoeleberis? thomsoni – Jellinek & Swanson 2003: 24, 25. Trachyleberis thomsoni? – Eglington 2006: 106, Figs 4L, M. Glencoeleberis? thomsoni – Ayress 2006: 370, Figs 6G-K, M, Table 1. Glencoeleberis? thomsoni – Brandão, Yasuhara, Irizuki & Horne 2013: 386.

Description. In specimens of both large and small forms of Glencoeleberis? thomsoni, and in illustrations from other authors (Plate 1) there are four discernable alignments of the tubercles. Three extend laterally along the carapace, they are: the ventral ala row terminating towards the posterior with a large, sometimes polyfurcate spine, the curving dorsal row commencing just forward of and above the subcentral tubercle and terminating postero- dorsally with a large spine that may be bi- or polyfurcate, and a curving postero-medial row of four or more tubercles behind the subcentral tubercle. The fourth alignment is a transverse row curving upwards from anterior of the subcentral tubercle to the large, semi-spherical eye tubercle. In most specimens all four rows of tubercles are on slightly raised, weakly-defined ribs. MPCs are straight to curving, some with medial thickening (Plate 1T–U).

Discussion. There are distinctive features of Glencoeleberis? thomsoni for consideration: 1. Alignment of the tubercles. 2. Occurrence of both large and small forms in Australian and New Zealand locations.

In considering allocation to Actinocythereis, alignment of tubercles in three lateral rows is present in both the large and small forms of Glencoeleberis? thomsoni, the degree of development of the ribs beneath is very slight, it is of the same order as seen in Actinocythereis tetrica (Brady 1880; from McKenzie & Pickett 1984; Plate 1W herein). However the thickening of the MPCs in both large and small forms of Glencoeleberis? thomsoni (Plate 1 Q, T, U) does not concur with Puri's diagnosis of Actinocythereis (1953) which required there to be no thickened portion of MPCs.

Although there is some similarity between Glencoeleberis? thomsoni and the Glencoeleberis taxa of Jellinek & Swanson (2003) in the alignments of tubercles behind the subcentral tubercle, difficulties are encountered when considering accommodating the various thomsoni taxa within Glencoeleberis, these are: 1. G.? thomsoni lack a distinctive ventral rib, they typically have a ventral row of well-developed, separate tubercles; 2. the four tubercles

187 antero-ventral to the sub-central tubercle are far more aggressively expressed than the Glencoeleberis taxa (Jellinek & Swanson 2003); 3. G.? thomsoni have a curving row of tubercles below the eye tubercle; 4. in the Australian large and small forms both straight and curving marginal pore canals (MPCs) occur, some with medial thickening, the MPCs for Glencoeleberis taxa (Jellinek & Swanson 2003) are straight and simple. In the absence of another, more suitable genus, and awaiting the revue foreshadowed by Brandão et al. (2013), the designation of interrogative Glencoeleberis has therefore been chosen, with reservation, for the thomsoni taxa.

Glencoeleberis? thomsoni may be a transitional form between Trachyleberis, Glencoeleberis and Actinocythereis. The observations by Warne & Whatley (1996) regarding the possible close relationship between Indo/Pacific Trachyleberis and Actinocythereis could be extended to include Glencoeleberis, and as the reassessment of other taxa removed from Trachyleberis (Brandão et al. 2013) progresses, many other affiliations should become clearer.

Cenozoic occurrences of Glencoeleberis? thomsoni range from Late Paleocene/Early Eocene– Early Miocene in New Zealand (Swanson, 1969; Ayress, 1993a, 1993b, 1995, 2006), and from Early Eocene–Late Oligocene/Early Miocene? in Australia.

Both small and large forms of Glencoeleberis? thomsoni have been found in New Zealand (Ayress 1993b, 1995, 2006) and Australian assemblages (Eglington 2006; Sections 2 and 3 herein). It seems very likely that the New Zealand small forms are the same variety as Glencoeleberis? thomsoni var. A, but synonymy is not assumed until direct comparison can be made. Occurrence of the two forms together in both southern Australian and New Zealand assemblages, accords with migration rather than having evolved separately.

Other Glencoeleberis? with similarities to G.? thomsoni are Glencoeleberis? cf. occultata Jellinek & Swanson (2003) previously referred to as "Trachyleberis thomsoni robust form" in Ayress (1993a, 2006) from New Zealand strata of Late Oligocene to Early Miocene age, and Glencoeleberis? thomsoni ayressi Milhau (1993), a large sized New Zealand subspecies from the Late Oligocene to Early Miocene age with an alignment of the tubercles similar to G.? thomsoni.

Non Trachyleberis aff. thomsoni of Majoran (1996a) is T. brevicosta major McKenzie, Reyment & Reyment (1991).

Material. More than 100 specimens.

Occurrence and age. Latrobe-1, Heywood-10, Narrawaturk-2, Yangery-1 bores, Rivernook, Castle Cove and Browns Creek outcrops; Pember Mudstone Member below Rivernook Member, Rivernook Member, Browns Creek Clays, Narrawaturk Formation, Gellibrand Marl; latest Paleocene/earliest Eocene to Late Oligocene/Early Miocene?.

Glencoeleberis? thomsoni (Hornibrook 1952) var. A Plate 1 F, J, M, P, T non Trachyleberis cf. careyi – McKenzie, Reyment & Reyment 1993: 105, Pl. 6, fig. 6. Actinocythereis sp. – Ayress 1993b: Fig. 3 L, Table 1. Trachyleberis thomsoni "small form" – Ayress 1995: Fig. 11.5 Glencoeleberis cf. armata Jellinek & Swanson 2003 – Ayress 2006: 370, Fig. 6L, N-P Trachyleberis thomsoni? – Eglington 2006: 106, Figs 4L, M, Tables 1–2. Glencoeleberis? thomsoni var. A – Eglington (Chapter 3 Taxonomy herein).

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Discussion. This taxon has the same shape and ornament as Glencoeleberis? thomsoni, but is considerably smaller, a "dwarf" form. Ayress (1993b) graphically demonstrated the two size ranges of Glencoeleberis? thomsoni. In the Victorian locations the large form of Glencoeleberis? thomsoni was found in more samples and overall was more abundant than G.? thomsoni var. A.

Actinocythereis sp. Ayress (1993b), Trachyleberis? thomsoni "small form" (Ayress 1995) and Glencoeleberis cf. armata Jellinek & Swanson 2003 (Ayress 2006) are almost certainly Glencoeleberis? thomsoni var. A. Non Trachyleberis cf. careyi McKenzie, Reyment & Reyment (1991) in McKenzie et al. (1993). These specimens are far smaller and possess a different arrangement of ornament when compared to Trachyleberis careyi collected by the author from Castle Cove and Browns Creek. The McKenzie et al. (1993) illustration compares very favourably with the author's specimens of Glencoeleberis? thomsoni from these two locations. There are no extant specimens from McKenzie et al. (1993) for comparison.

Measurements. Length of adults 0.7–0.85 mm, height 0.43–0.47 mm.

Material. 35 specimens.

Occurrence and age. Latrobe-1, Rivernook and Princetown Members, Trochocyathus and Turritella beds; Narrawaturk-2 bore, Narrawaturk Formation; outcropping Rivernook Member; Browns Creek Clays at Castle Cove and Browns Creek; Early Eocene–Oligocene.

Glencoeleberis? sp. Plate 1N

Description. A large, thick-shelled, sub-triangular trachyleberidid with convex anterior margin; ventral and dorsal margins straight, sloping towards the medially positioned, angular posterior margin. Maximum height just behind the eye tubercle; maximum length medial. The surface is heavily ornamented with robust tubercles aligned in three lateral rows raised on ribs: one row along the ventral ala, one dorsally from behind the eye tubercle to the postero- dorsal angle, the third postero-medial from the subcentral tubercle. A fourth alignment curves from in front and above the subcentral tubercle to the eye tubercle; it is also on a low, broad rib. Anterior and posterior margins bear spines. The surface, apart from the margins, also displays dense micro-reticulation. Internally, the CMS consists of a vertical column of four rectangular adductors and a J-shaped frontal scar.

Discussion. These female specimens are slightly smaller, more robust, the ornament much heavier, the ribs beneath the aligned tubercles more definite, and the micro-reticulation (Plate 2A-D) is quite different in form and arrangement to that of Glencoeleberis? thomsoni. More

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Plate 1.

A-D. Trachyleberis careyi McKenzie, Reyment & Reyment (1991). A. MRV (from McKenzie et al. 1991, Plate 7, fig. 11), L= ~ 0.93 mm. B. FRV (from McKenzie et al. 1991, Plate 7, fig. 12), L= ~ 0.9 mm. C. D. MLV, FRV, Browns Creek Clays, Castle Cove. E. Glencoeleberis? thomsoni (Hornibrook 1952), (non Trachyleberis cf. careyi from McKenzie et al. 1993, Plate 6, fig. 6), MLV, L=0.89 mm, H=0.46 mm. F. Glencoeleberis? thomsoni var. A, FRV (Section 3, Plate 2, fig. Q herein), Rivernook Member, Rivernook. G. Glencoeleberis? thomsoni large form, LVM, L=1.1 mm, H = 0.56 mm, Browns Creek Clays, Castle Cove. H. Glencoeleberis? thomsoni, LV, L=1.0 mm (from Majoran, 1996a, Fig. 9L). I. Glencoeleberis? thomsoni Hornibrook (1952, from Hornibrook 1952, Plate 3, fig. 40), RV, L = 1.3 mm. J. Glencoeleberis? thomsoni var. A, adult LV (Section 3, Plate 2, fig. N herein), FLV, Trochocyathus Bed, Dilwyn Formation, Latrobe-1 bore. K. Glencoeleberis? thomsoni, MLV, L=1.28 mm (from Ayress, 1993a, Fig. 9Q). L. Glencoeleberis? cf. occultata Jellinek & Swanson (2003), MLV, L=1.25 mm (previously Trachyleberis thomsoni robust form, from Ayress, 1993a, Fig. 9R). M. Glencoeleberis? thomsoni var. A, FRV, (Section 3 herein), Rivernook Member Rivernook. N. Glencoeleberis? sp. FLV, Browns Creek Clays, Castle Cove. O. Glencoeleberi? thomsoni (Hornibrook 1952, from Hornibrook 1952, Plate 3, fig. 47), L = 1.26 mm. P. Glencoeleberis? thomsoni var. A, RV dorsal, Princetown Member, Latrobe-1. Q. Glencoeleberis? thomsoni, large form, inner marginal zone, RV anterior, Browns Creek Clays, Castle Cove. R. Glencoeleberis? thomsoni small form (from Ayress 1995 Fig. 11.5), MRV. S. Actinocythereis tetrica (Brady 1880; from McKenzie & Pickett 1984, Fig. 4CC), MRV. T. Glencoeleberis? thomsoni var. A, inner marginal zone, LV anterior, Rivernook Member, Rivernook. U. Glencoeleberis? thomsoni large form, inner marginal zone, LV anterior, Browns Creek Clays, Castle Cove. V. ?Actinocythereis sp. A, (from Neil 1994, Plate 1, fig. 4), ALV. W. A. tetrica (Brady 1880; from McKenzie & Pickett 1984, Fig. 4EE), FLV.

All scale bars = 100 µ.

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material is required for comparison.

Measurements. Length 0.91–0.99 mm, height 0.50–0.53 mm.

Material. Twenty specimens.

Occurrence and age. Browns Creek Clays, Browns Creek and Castle Cove; Late Eocene.

Genus Trachyleberis Brady 1898 Trachyleberis careyi McKenzie, Reyment & Reyment 1991 Plate 1A-D

Trachyleberis careyi McKenzie, Reyment & Reyment 1991: 169–170, Pl. 7, figs 11, 12, Pl. 10, figs 13, 14. non Trachyleberis cf. careyi – McKenzie, Reyment & Reyment 1993: 105, Pl. 6, fig. 6; [is G.? thomsoni Hornibrook 1952] Trachyleberis careyi – Neil 1997: 180, Figs 7A–F, H, J. Trachyleberis careyi – Eglington 2006: 105-106, Figs 4J, P–Q.

Description. A very large Trachyleberis with an ornament of spines and tubercles, sexually dimorphic, in lateral view males relatively longer and narrower than females.

Discussion. McKenzie et al. (1991) found this species in Late Oligocene and Miocene strata of southern Victoria. They also identified 16 specimens from Castle Cove, Browns Creek and Bells Headland (McKenzie et al. 1993) as Trachyleberis cf. careyi but the MLV they illustrated is only 0.89 mm long, and the ornament, and outline in lateral view do not accord with their illustrations (McKenzie et al. 1991) of T. careyi. The author has found numerous specimens of non Trachyleberis cf. careyi at Castle Cove and Browns Creek that display the shape and alignment of tubercles of G.? thomsoni Hornibrook (1952), plus a smaller number of specimens of very different appearance that conform to Trachyleberis careyi, although the specimens from Castle Cove and Narrawaturk-2 bore are consistently far larger than the measurements given for T. careyi McKenzie et al. (1991).

Measurements. Length 1.44–1.73 mm, height 0.75–0.85 mm.

Occurrence and age. Browns Creek Clays and Lower Glen Aire Clays, Castle Cove, Late Eocene–Early Oligocene. Narawaturk Formation, Narrawaturk-2 bore (582–584 m), Late Eocene (Taylor 1964b). Pebble Point Formation, Late Paleocene, (Neil 1997); Bells Headland, Victoria, Late Oligocene, Point Addis Limestone, Miocene (McKenzie et al. 1991).

CONCLUSION

Glencoeleberis? thomsoni Hornibrook (1952) has diagnostic features of Actinocythereis, Glencoeleberis and Trachyleberis. Its generic location is questioned because of the alignment of tubercles, the ribs beneath the rows of tubercles are sometimes very minimal, and there is thickening of the marginal pore canals. Glencoeleberis? thomsoni is morphologically diverse, including a dwarf form; both large and dwarf forms are present in Australian and New Zealand assemblages.

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The combination of a benthic lifestyle, and the endemism of many Australian and New Zealand ostracod taxa provides a useful tool for palaeogeographic reconstruction and interpretation. The occurrence of the exclusively regional Glencoeleberis? thomsoni Hornibrook (1952) in both Australian and New Zealand latest Paleocene/earliest Eocene marine sediments requires there to have been a marine connection allowing migration between the Australo-Antarctic Gulf and the Tasman Sea. Lacking evidence for any other viable route, this link must have been in the vicinity of the South Tasman Saddle.

ACKNOWLEDGEMENTS

Grateful thanks for extensive supervisory guidance, support and editorial comment are extended to Kelsie Dadd, John A. Talent and Ruth Mawson of Earth and Planetary Sciences, Macquarie University. The comments and recommendations of the referees Michael Ayress, Alan Lord and Mark Warne are deeply appreciated and grateful thanks extended.

REFERENCES

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SECTION 9

THE ANOMALOUS CYTHERELLA POSTATYPICA (OSTRACODA:CRUSTACEA) AS EVIDENCE FOR A LATE PALEOCENE SOUTH-FLOWING CURRENT DOWN THE WEST COAST OF AUSTRALIA

COL EGLINGTON

Department of Earth and Planetary Sciences, Macquarie University, Sydney, NSW 2109, Australia. [email protected]

EGLINGTON, C. The anomalous Cytherella postatypica (Ostracoda: Crustacea) as evidence for a Late Paleocene south-flowing current down the west coast of Australia.

Key Words. Paleocene, Ostracoda, Cytherella postatypica, Wangerrip Group, Pebble Point Formation, Otway Basin, Australia, Australo-Antarctic Gulf, proto-Leeuwin Current.

ABSTRACT

A benthic marine ostracod with anomalous valve overlap, Cytherella postatypica sp. nov., found in the Late Paleocene strata of southwestern Victoria, provides evidence for an early south-flowing current down the west coast of Western Australia. Its ancestor, Cytherella atypica Bate (1972), the earliest platycopid to display left-over-right valve overlap, was endemic in the Late Cretaceous of the Carnarvon Basin of Western Australia. Presence of Cytherella postatypica in the Australo-Antarctic Gulf by the Late Paleocene is evidence of a south-flowing current that enabled the non-swimming C. atypica to migrate from the Carnarvon Basin and for its closely related descendant C. postatypica to appear in the Australo-Antarctic Gulf in and above the Late Paleocene Pebble Point Formation and Pember Mudstone of the Wangerrip Group. The southern distribution of this lineage accords with the presence of a Western Australian south-flowing current existing no later than Paleocene, much earlier than the Leeuwin Current that replaced the north-flowing West Australian Current in the Early Oligocene. This proposed current may have been near-shore, flowing counter to and inside the West Australian Current; it may have been episodic.

INTRODUCTION

The incomplete stratigraphy of the Paleocene-Eocene Chron 24 interval within and on the margins of basins, as well as the dearth of deep-sea records, present major impediments to Paleogene studies (Aubrey 1998). This overall lack of data, plus the paucity of Early Paleogene outcrops in southeastern Australia, coupled with poor recovery of calcitic microfossils when present in the Otway Basin, have handicapped developing a synthesis of the palaeoenvironment and geological history for the Australo-Antarctic region. As ostracod (Crustacea) genera evolve rapidly and are limited ecologically by the depths and temperatures they can tolerate, the combination of rapid rates of evolution and high ecological sensitivity makes their assemblages highly useful as biostratigraphic and palaeoecologic tools (Kornicker 1958; Van Morkhoven 1962; McKenzie 1964; Puri 1966; Swain 1967). Ostracods obtained from this Paleogene interval in Australia, are thus potentially valuable. The Pebble Point Formation in the Otway Basin, southeastern Australia, has produced Australia’s only sizeable Late Paleocene ostracod assemblage (Neil 1997). An additional seven specimens are now reported from the Late Paleocene Pember Mudstone Member in Heywood-10 bore (Section 3 herein) plus a single specimen reported earlier from the latest Paleocene – earliest Eocene

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Pember Mudstone Member in Latrobe-1 bore (Eglington 2006). These assemblages, and those of the Early–Late Eocene (Sections 2–5 herein), have the capacity to augment palaeoenvironmental and palaeogeographic interpretations obtained from other microfossil groups (Sections 5–8 herein).

The presence of a Late Paleocene ostracod species within the northeastern AAG, and its close affiliation with a Late Cretaceous taxon from the Carnarvon Basin (Fig. 4), Western Australia (Section 4 herein), was revealed in assemblages from Otway Basin locations (Eglington 2006; Sections 2–5 herein). This paper examines the palaeogeographic implications of this relationship.

Fig. 1. Locations and structures, Otway Basin, Victoria, Australia (after Wopfner & Douglas 1971).

Fig. 2. Outcrop and bore locations in the Princetown area, Victoria (Eglington 2006).

The Victorian Otway Basin is one of a series of structures formed across southern Australia by rifting of Gondwana. East-west trending, approximately 500 km long, extending laterally both onshore and offshore, it contains a thick Mesozoic and Cenozoic sequence. The outcropping Pebble Point Formation and Rivernook Member, and the Latrobe-1 bore, are located in the eastern end of the Port Campbell Embayment between the Warrnambool and

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Otway Ranges Highs, structural units within the basin (Figs 1 & 2) (Wopfner & Douglas 1971). Heywood-10 bore is within the Tyrendarra Embayment (Figs 1 and 2) (Wopfner & Douglas 1971; Abele 1976). Resting unconformably on Cretaceous sedimentary rocks, the Wangerrip Group is a sequence of Paleocene to Middle Eocene sedimentary rocks, largely paralic marine to brackish, with sequences of inner estuarine channel sandstone (McGowran 1965; Arditto 1995; Holdgate & Gallagher 2003). Its basal unit is the mainly transgressive shallow marine Late Paleocene Pebble Point Formation (Holdgate & Gallagher 2003) with, above it, the latest Paleocene–earliest Eocene Pember Mudstone Member, and the predominantly Eocene Dilwyn Formation (Holdgate & Gallagher 2003). The Rivernook Member is an Early Eocene (Ypresian), upper Chron 24, P6b zone in fine-grained siliciclastic, sandy siltstone to clayey sandstone within the Dilwyn Formation occurring in coastal exposures and in the Latrobe-1 bore (Baker 1950, 1953; Taylor 1965; McGowran 1965, 1970; McGowran et al. 2000; Eglington 2006).

The Carnarvon Basin, situated in the northwest of Western Australia (Fig. 4), is the main structural feature of the North West Shelf; covers a total of 650,000 km2 (Fig. 4). The Carnarvon Basin strata from which Bate (1972) extracted Cytherella atypica Bate (1972) are within the Toolonga Calcilutite/Gingin Chalk/Coolyena Group–a Late Cretaceous (Santonia – Campanian, 85–75 Ma) sedimentary rock composed predominately of chalky calcisiltite to calcilutite; it was deposited in a shallow marine open shelf environment (Belford 1960; Bate 1972).

Palaeogeography

The Australo-Antarctic break-up of Gondwana commenced in the Late Cretaceous and was well underway by the end of the Paleocene with separation of the Antarctic and Australian blocks creating the Australo-Antarctic Gulf (AAG, Fig. 4) (Duddy 2003; Cande & Stock 2004). By the Early Eocene this long, narrow sea was probably some 1,500 km long (east– west); estimates of its width (north–south) vary from as little as 200 km (Shafik 1990) up to at least 600 km and possibly over 1000 km wide (Cande & Stock 2004). It was an almost completely enclosed, deep marine basin, open at the western end to the inflow of warm surface waters from the Indian Ocean, with extensive shallow continental shelves. The eastern end was part of a broad, shallow, continental shelf with restricted circulation in some parts and particularly poor ventilation. A west-east current is assumed to have flowed along the northern region, part of a weak, clockwise gyre (Fig. 4) (Exon et al. 2004d).

In the Early Eocene the Princetown area was located towards the eastern end of the AAG on the shallow, northern continental shelf at about 60°S latitude and was subjected to cyclic marine transgressions/ingressions and regressions (Deighton et al. 1976; Kennett & Exon 2004).

Prior to the early Oligocene establishment of the Leeuwin Current, the West Australian Current flowed from southwest to north up the western coast of the Australian continental block (McGowran et al. 1997b; McGowran et al. 2000; Wyrwoll et al. 2009). Today the Leeuwin Current is a rapid, south-flowing current off the Western Australian coast that commences off North West Cape, is approximately 5,500 km long and meanders along the continental margin, rounding Cape Leeuwin to enter the Great Australian Bight. It then flows eastwards to the southern tip of Tasmania (Collins 1995; Deng et al. 2008). Tectonic and climatic events have modified the current periodically since its inception; this is still occurring with seasonal and inter-annual variations in its transport load (Deng et al. 2008). Because the Leeuwin Current carries warm water to the temperate and polar regions, its influence on past, present and future climate, and on western and southern Australian marine communities is of

201 great interest to researchers in climate change, palaeoecology, and marine biology (Collins 1995; McGowran 1997a, 1997b; Li et al. 1999; Exon et al. 2004; Huber et al. 2004; Greenstein & Pandolfi 2008; Feng 2009; Wyrwoll et al. 2009).

RESULTS

Migration pattern as evidence for an earlier West Australian south-flowing coastal current

An anomalous cytherellid (Ostracoda: Crustacea: Podocopida: Platycopa: Cytherellidae), Cytherella atypica Bate (1972), first appeared in the Carnarvon Basin, northwest Western Australia in the Late Cretaceous (Figs 3 and 4). Cytherella. atypica displays a reversed (left- over-right) valve overlap; this is unique to Cytherella within the Australia–New Zealand region (Bate 1972; Milhau 1993; Swanson et al. 2005; Eglington 2006; Section 4 herein). Cytherella postatypica Eglington (Section 4 herein), a direct descendent of C. atypica, possesses the same valve overlap. Cytherella postatypica first appeared in the AAG during the Late Paleocene in outcrops of the Pebble Point Formation (Neil 1997; Eglington 2006) and Pember Mudstone in Heywood-10 bore (Section 3 herein), then in the latest Paleocene– earliest Eocene Pember Mudstone Member in Latrobe-1 bore (Fig. 3). The taxon is found in Early Eocene assemblages in the Dilwyn Formation in outcrop at Rivernook and in Latrobe-1 bore, Late Eocene Browns Creek Clays at Browns Creek and Castle Cove, and is widespread through the Oligocene into the Miocene (Section 4 herein) (Fig. 3).

C. aff. postatypica C. sp. 3 L. Eocene Browns Creek Browns Creek Castle Cove Castle Cove

E. Eocene Latrobe-1

Heywood-10

L. Paleocene C. postatypica Pebble Point

Late Cretaceous C. atypica & C. aff. atypica Western Australia

Fig. 3. Paleocene–Eocene range and distribution of Cytherella atypica Bate (1972), C. postatypica sp. nov. and related sinistral Cytherella.

Other taxa found first in the West Australian Cretaceous then subsequently in the northeastern AAG during the Late Paleocene or in close proximity to the Paleocene/Eocene boundary are the genera Munseyella (Neale 1975; Neil 1997; Eglington Sections 2 and 3 herein), Maddocksella (Bate 1972;Neil 1997), Neonesidea (Bate 1972; Neale 1975; Neil 1997; Eglington Sections 2 and 3 herein), Scepticocythereis (Bate 1972; Neale 1975; Neil 1997; Eglington Sections 3 herein) and the species Premunseyella imperfecta (Bate 1972; Neale 1975; Neil 1997).

From the Late Cretaceous onwards there is no evidence of a seaway across the continental landmass linking the Carnarvon Basin and Southern Victoria (Stuckmeyer & Totterdell 1990; Johnson 2004). The only path of migration from the Carnarvon Basin into the Otway Basin for the benthic Cytherella atypica or its descendant would have been down the West Australian coast (Fig. 4). To have spread such a distance would be most unlikely if it were against the strong, prevailing, south-to-north West Australian Current. Cytherella atypica

202 most probably migrated from the Carnarvon Basin towards the AAG, aided by a south- flowing current no later than Paleocene, and evolved into C. postatypica, appearing in the

Fig. 4. Tectonic and oceanographic reconstructions of the Australo- Antarctic Gulf (AAG) and Carnarvon Basin location, Early Eocene. Block arrow indicates the direction of the proposed Paleocene current flowing south along the West Australian coast. Narrow arrows indicate the main current flow in the Early Eocene AAG (adapted from McGowran et al. 1997b; Cande & Stock 2004; Exon, Kennett & Malone 2004d); OB = Otway Basin.

Pebble Point area by the Late Paleocene. This is much earlier than the first suggested appearance of the current in the late Middle Eocene (McGowran et al. 1997). The current (Fig. 4) could have been either a Proto-Leeuwin Current, or a near-shore flow that ran inside and counter to the West Australian Current. From the west coast the current would have fed into the entrance of the AAG becoming a part of the northern arm of the clockwise gyre as it flowed along the southern edge of the Australian continental margin. This Western Australian current may have been spasmodic, or have operated only for a period of sufficient duration to enable migration of the taxon into the AAG. The abundance of Cytherella postatypica in warm, shallow water assemblages (Section 5 herein) accords with this having been the preferred environment for the lineage; its migration route most likely involved such inner shelf/near shore environments, with transport by one or a series of near shore currents running counter to the West Australian Current.

CONCLUSION

The proposed current off the West Australian coast provides a mechanism for the southern migration of the ostracod species Cytherella atypica Bate (1972), resulting in the appearance of its descendants in the AAG. The first of these to be recorded is the closely-related Cytherella postatypica, found in the Late Paleocene Pebble Point Formation in the Otway Basin, Victoria.

Given the extensive exploratory offshore drilling for oil in the basins of the northern AAG, and the probability of ostracod assemblages being found in at least some of them, there is the potential for Ostracoda to play a much more significant role in palaeoenvironmental and palaeogeographic analysis and interpretation.

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ACKNOWLEDGEMENTS

Grateful thanks for extensive supervisory guidance, support and editorial comment are extended to Kelsie Dadd, John A. Talent and Ruth Mawson of Earth and Planetary Sciences, Macquarie University. The comments and recommendations of the referees Michael Ayress, Alan Lord and Mark Warne are deeply appreciated and grateful thanks extended.

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SECTION 10

ADAPTATION OF BIOLOGICAL MICROSCOPY AND DIGITAL EDITING TECHNIQUES TO MICROPALAEONTOLOGY COL EGLINGTON

Department of Earth and Planetary Sciences, Macquarie University, Sydney, NSW 2109, Australia. [email protected]

EGLINGTON, C. Adaptation of biological microscopy and digital editing techniques to micropalaeontology.

Key Words. Micropalaeontology, microscopy, Ostracoda, digital editing, Photoshop.

ABSTRACT

In the course of research on Early Cenozoic Ostracoda (Crustacea) a method for digital imaging and enhancement of microscopic specimens was discovered, developed and procedures established. The technique is used, in conjunction with adapted conventional biological practices of staining, liquid emersion, transmitted light and dark field illumination, to produce highly contrasting colour images of features such as central muscle scars that are otherwise difficult to observe or scan electron microscope (SEM) photograph.

INTRODUCTION

Until the advent of digital technology, micropalaeontologists relied on hand drawings (usually with a camera lucida), electron microscope scans or conventional photography to record their specimens. Drawings are time consuming, conventional microscope photography required wet processing of film with (usually) poor pictures that could only be minimally enhanced in the darkroom; the cost and time needed for electron microscope scanning still prohibits its use for recording large numbers of specimens for reference purposes, thus restricting it to publishing of illustrations. Digital photography has provided palaeontologists with a method for capturing and storing large quantities of images for no more than the cost of equipment and software. It was from the need to obtain pictures of thousands of specimens for taxonomic evaluation that this study arose. The purpose of this paper is to share this knowledge and experience with other workers in palaeontology or biology.

The conventional microscopy and digital techniques described have been developed for studying assemblages of Ostracoda (Crustacea) from the Early Tertiary of the Otway Basin in southern Victoria, Australia (Eglington 2006). The large numbers of specimens and taxa being examined has necessitated a system for recording and comparing material in a fast, efficient and economic manner. In addition, some important assemblages were very small with rare, key specimens poorly preserved, or with significant diagnostic features partially obscured or not observable. These impediments provided the impetus to find techniques for maximising data collected and its analysis. The author has drawn from his background in both biology and digital photography to utilise and modify established practices and to develop new approaches. Whereas the digital editing methodology was applied only to ostracods, it is also applicable to other microfossils, as well as to biological specimens. The advantage of the digital approach is that it does not require any processing of the specimens, thus reducing risk of damage.

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METHODOLOGY

Conventional biological techniques applied to fossils

Staining. Biological staining is used for differentially enhancing the appearance of plant or animal tissues for optical microscope viewing or photography. It relies on differences in the chemical and physical properties of cells or cell components, staining them darker or lighter, or a different colour, compared to other features. When applied to calcitic fossil ostracods, particularly the ornamented taxa, the dye will stain sediment-filled pits or areas that are more porous. In less ornamented forms, the dye can darken the less compact area around the denser (therefore lighter) central muscle scars (CMS).

The ostracod carapace or valve is soaked for a few seconds in a drop of aqueous methylene blue solution on a glass slide or small glass petri dish under the microscope (Fig. 1). The concentration should not be excessive, otherwise an opaque “metallic” sheen remains on the specimen’s surface when dry. After soaking, excess dye is removed with water on a fine (00- sable) brush while under observation. A stronger solution producing the metallic sheen can be useful for viewing surfaces because the incident light, especially if at a low angle to the specimen surface, is reflected, allowing very fine features to be observed. Staining in no way inhibits electron micrographs (SEM).

Fig. 1. A small, untreated, translucent, Early Cenozoic Callistocythere carapace (left) under incident light. Same species, (different specimen) viewed simultaneously with incident and transmitted light has been stained with methylene blue (middle), then digitally enhanced (right).

Transmitted light microscopy. As most micropalaeontologists study only hard fossil remains, the main tool is the stereo incident-light microscope; many rarely or never use transmitted light biological microscopes, and may be unaware of the advantages these possess, including far higher magnification, often finer focussing, and the enhanced internal detail visible in transparent or translucent specimens. With ostracods, this is particularly applicable to observations of marginal pore canals (MPC), central muscle scars (CMS), optical sinuses and hinge structure. If incident light is required for surface observations, this is also easily achieved using dark field illumination (no transmitted light) or a combination of both.

Sky illumination (not direct sunlight) reflected by the sub-stage mirror through the specimen will often give a sharp, clean image for transmitted light observations compared with artificial light which may produce halos and other optical effects – these can be difficult to eliminate with condenser adjustments and filters such as blue filters that reduce the light and hence reduce visibility. A useful magnification range with transmitted light for ostracod specimens is 50 – 600x using 10x and 40x objectives with 5x, 10x and 15x oculars. Loss of depth of field at higher magnifications will require use of fine-focus racking.

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Liquid immersion with transmitted light. Observing material in liquid to reduce the refractive index differential and enhance transparency is well established in biology but not common in palaeontology, particularly with workers lacking a background in techniques in biology.

By immersing a stained or unstained shell in water for observation using transmitted light additional details are observable. Liquids such as glycerine or eucalyptus oil evaporate more slowly but may be difficult to clean off, leaving the shell sticky and vulnerable to damage during cleaning. For smooth valves with hard-to-see CMS, place the valve in a drop of water with the valve wet inside and out, and view separately with reflected and transmitted light. If the CMS are still not visible, then careful observation while the water evaporates will often reveal a split second view of the CMS before becoming completely dry.

Liquid immersion with incident light. The presence of fine crenulation on the median hinge element (bar) can be impossible to verify without a SCAN. The following method will frequently answer this question.

Have the internal view of the valve uppermost on a slide in a drop of water. Using only reflected light, observe the hinge area as the drop evaporates. At a certain point the edges of the shell will be at the surface of the drop with the smoothness of the surface only distorted by irregularities along the valve edges. This is aided by the concave meniscus produced by surface tension of the water inside the valve and the convex meniscus outside. A low angle of reflected light across this air-water interface will reveal the presence of a crenulated hinge bar as a series of fine serrations at the water surface. Orientation of the hinge bar to the light source is critical, so it is important to rotate the slide/stage horizontally and observe from all angles.

Equipment

The Olympus Camedia C-5060 Wide Zoom Digital Compact Camera with microscope attachment plus electronic remote control RM-2 was used for all digital photography. The remote control eliminates any camera movement. Settings for the camera: no flash and highest aperture (minimum opening). Other settings such as light meter, manual, automatic and macro focus should be experimented with, as they will vary according to the particular specimens being photographed, their background, depth of field and the light source.

Digital editing

The following process is suitable for enhancing digital images of specimens (stained or unstained). It relies on the different physical properties of the material photographed and their effects on the light transmitted through or reflected from the specimen. The resulting image is very similar to one that has been differentially stained. The deliberately produced unnatural contrasting colours can greatly emphasise hard-to-see internal features such as CMS and marginal pore canals. Either Adobe Photoshop or Photoshop Elements may be used, though the author has favoured Photoshop Elements due to its ease of use and the flexibility of the Quick Edit tools, in particular Smart Fix. Versions used were Elements 7 and Photoshop CS3. Photoshop Elements is an extremely powerful and sophisticated program that has taken many of the best features of Photoshop CS, leaving out those of use only to professional photographers and graphic artists; that it provides some of its own extremely efficient tools should not be underestimated. Some tools that were initially available only in ‘Elements’ have since been incorporated in later versions of CS.

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Theory

Levels histogram. In Photoshop, the Levels histogram (Fig. 2) reduces the image to a greyscale graph showing the full range of values from 0–255 (black = 0, white = 255); the bars indicate the number of pixels at each of these 266 points (Rose 2002; Eismann & Duggan 2008).

Fig. 2. Photoshop Levels histogram of an unedited ostracod carapace SCAN (Cytherella pinnata McKenzie, Reyment & Reyment 1993) showing most of data in the darker region of the chart towards the 0/left end. The mid- range tapers off into the lighter values with no white present (255/far right).

Contrast. Contrast is the difference in brightness between tonal areas. Adjustments to the lighting balance are usually necessary (Fig. 3) but if excessive, will result in clipping. Clipping occurs when highlights or shadow values are adjusted so much they become pure

Fig. 3. The image has been Levels-adjusted for better contrast, the histogram appears spiky with gaps due to it now being spread over the full range 0–255 once the left and right ends were removed, but little data have been lost.

Fig. 4. The image has been over-adjusted, it has white/highlights and black areas from which all data have been lost, the histogram is crammed (clipped) against the 0 (left) and 255 (right) ends of the graph rather than displaying the tails tapering off as in Fig. 3.

212 white or pure black (Rose 2002), therefore data will have been lost from the lightest or darkest areas in the picture and hence from the corresponding end of the Lighting – Levels histogram. The histogram will appear jammed against the end and not exhibit a gradual taper- off (Fig. 4). The image is ‘blown out’ in these tonal areas.

Sharpening. The Sharpen tool/command heightens the difference between adjacent areas at their boundary. Photoshop finds contrasting edges, compares the adjacent pixels and then increases their dissimilarity (Eismann & Duggan 2008); it will clump similar contiguous pixels together and differentiate them from neighbouring dissimilar pixels. The standard sharpening effect reduces the graduation or tonal appearance across a picture resulting in an overall graininess (Fig. 5), more strongly emphasised edges for component images and thus enhances the difference between adjoining areas. It will result in data-loss, as seen in the “after” histogram (Fig. 5).

Fig. 5. The image (top), cropped from Fig. 3, has then been sharpened (bottom) resulting in loss of peaks/data as shown in its histogram. The single bars at 0 (left) and 255 (right) represent the areas of pure black and pure white, they are significantly higher than previously, indicating the extent to which differentiation resulting from sharpening has pushed values into these two zones.

Reducing loss of image data. As techniques such as sharpening and Smart Fix result in loss of data it is important to commence with a photograph of reasonable resolution but it is not essential that it be maximum resolution. It need not be TIFF or RAW capture, JPG/JPEG is usually adequate. In order to preserve the original image, it is suggested either of the following precautions be adopted:  Use a copy of the original image for editing.  Use layers and do all editing on them. Kloskowski (2008) is particularly useful regarding this Photoshop feature.

The second method has the disadvantage of being vulnerable to accidental disposal of the background layer or of merging it with other layers. As layers only operate in PDF and TIFF formats, if the file is inadvertently saved only in JPEG/JPG all the layers will merge irretrievably.

Emulating biological staining with Quick Edit. The Smart Fix – Auto tool and Levels – Auto tool in Photoshop Essentials’ Quick Edit are the keys to the process that digitally imitates

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biological staining of specimens. This method produces particularly good results for transparent/translucent material or for images of ornamented specimens with very little contrast. For a better appreciate of these effects, on-line colour version of the illustrations provided in greyscale for publication should be viewed.

Procedure – Photoshop Elements. The following procedure usually work best in the order presented though sometimes an image benefits from changing the sequence or omitting some steps.

1. Open Edit, import image.

2. Either open Levels histogram (Ctrl+L) and adjust or 3. in Quick Edit adjust lighting using Shadows/Highlights/Contrast sliders (but not the Auto adjustment button), however this is not as accurate as using the Levels histogram (Step 2).

4. In General Fixes – Smart Fix use Auto button.

5. In Quick Edit use Sharpen – Auto as set or enhance slightly by shifting slider to right. This should be done conservatively to reduce loss of detail or overly contrasting distortions within the image. Undo if found to not enhance the image.

6. Use Levels – Auto button, (may be positioned in the Lighting box), the result is usually a complete change of colours that are much more strongly contrasting, hence easier to see, particularly if the image is to be used as a base layer for a drawing.

7. Return to Full Edit and use Enhance – Adjust Lighting – Levels [Ctrl+L] to adjust again the Levels histogram, in particular the middle (mid range) slider, to tweak contrast. It is good practice to carry out this step; if no change is required cancel the adjustment or choose Reset.

8. Smart Fix Auto and Levels Auto (Steps 4 and 6) can be repeated to increase the effect but each time will reduce the quality of the image.

9. If saving in JPEG choose maximum quality, for TIFF select image compression –

none.

Fig. 6. A small, left valve internal view of a transparent Argilloecia sp. (left) has been digitally enhanced (middle) then the central muscle scars (CMS ) area cropped (right) and further developed using Levels – Auto button in Quick Edit.

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Fig. 7. Valve of an Early Tertiary Glencoeleberis? thomsoni immersed in water and viewed under biological microscope using transmitted light reflected from the sky (left). Image cropped and enlarged to view anterior marginal zone (middle) then edited (right) as described (steps 2, 4, 6, 7). All images have been converted to greyscale.

Procedure – Photoshop CS3. Similar results can be obtained in Photoshop CS. Import image then use following steps: Image – Adjustments – Auto Levels [Shift+Ctrl+L]. This step can be repeated as often as needed then adjust contrast further if required – Image – Adjustments

– Levels [Ctrl+L].

Fig. 8. Marginal pore canals from a Recent Paracypris sp. fragment (left) before (middle) and after digital enhancement (right).

General comments

Later versions of the software will have been in use more recently, however the general principles will still apply, though individual tool names and functions may have changed slightly. Adaptation should not be difficult if the theory is understood. On-line forums can answer virtually every digital editing query despite the somewhat esoteric requirements of the palaeontologist or biologist. It is hoped that the information and ideas presented here will inspire further experimentation and expand our understanding and use of these aids to research.

ACKNOWLEDGEMENTS

Grateful thanks for extensive supervisory guidance, support and editorial comment are extended to Kelsie Dadd, John A. Talent and Ruth Mawson of Earth and Planetary Sciences, Macquarie University. The comments and recommendations of the referees Michael Ayress, Alan Lord and Mark Warne are deeply appreciated and grateful thanks extended.

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REFERENCES

ALSHEIMER, L. 2007. Black and White in Photoshop CS3 and Photoshop Lightroom. Focal Press Elsevier, Oxford UK, Burlington MA, 241 pp. BLATNER, D., CHAVEZ, C. & FRASER, B. 2008. Real World Adobe Photoshop CS3 Industrial-Strength Productions. Peachpit Press, Berkeley, 750 pp. EGLINGTON, C., 2006. Paleogene Ostracoda (Crustacea) from the Wangerrip Group, Latrobe-1 bore, Otway Basin, Victoria, Australia. Proceedings of the Royal Society of Victoria. 118(1): 87-111. EISMANN, K. 2005. Photoshop Masking and Composition. New Riders, Berkeley, 544 pp. EISMANN, K. 2006. Photoshop Restoration and Retouching. New Riders, Berkeley, 460 pp. EISMANN, K. & DUGGAN, S. 2008. The Creative Digital Darkroom. O’Reilly, Sebastapol, 411 pp. EVENING, M. 2004. Adobe Photoshop CS3 for Photographers. Focal Press Elsevier, Oxford UK, Burlington MA, 554 pp. KLOSKOWSKI, M. 2008. The Complete Guide to Photoshop’s Most Powerful Feature Layers. Peachpit Press, Berkeley, 255 pp. ROSE, C. 2002. Sams Teach Yourself Adobe Photoshop 7 in 24 Hours. Sams, Indianapolis, 462 pp.

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SECTION 11

CONCLUSION

Outcomes

The aims of the study were to collect and describe Paleogene Otway Basin Ostracoda (Crustacea) from locations not previously sampled for ostracods, and to use these taxa and assemblages for biostratigraphic, palaeoenvironmental and palaeogeographic interpretation. These aims have been met as follows:

New assemblages, biostratigraphy and taxonomy

 Described 29 Paleogene ostracod assemblages (128 taxa) from three new southern Victorian locations: Latrobe-1 and Heywood-10 boreholes, and from a Rivernook outcrop.

 Described ostracod assemblages from stratigraphic units not previously investigated. These are the Wangerrip Group/Dilwyn Formation, the Nirranda Group/Narrawaturk Formation, and the Late Oligocene section of the Heytesbury Group/Gellibrand Marl.

 Identified ten new species, subspecies and varieties of Ostracoda: Neobuntonia taylori sp. nov., Tasmanocypris? latrobensis sp. nov., Cytherella batei sp. nov., Cytherella postatypica sp. nov., Cytherella conturba sp. nov., Aversovalva hasta sp. nov., Xestoleberis heywoodensis sp. nov., Oculocytheropteron ayressi Majoran, 1997 varius subsp. nov. and two “dwarf” varieties, Neonesidea australis var. A and Glencoeleberis? thomsoni var. A. Fifty-nine taxa have been left in open nomenclature awaiting further information from additional and, preferably, better material. The descriptions and illustrations of other taxa have been supplemented.

 Investigated Cytherella with a reversed valve overlap (left valve > right valve), described new taxa, presented an explanation of their migration, evolution and relationships, and identified issues that still need to be resolved.

 Described the first example of a platycopid species having both normal and reversed valve overlap (Cytherella conturba sp. nov.), and, after probing the genus Inversacytherella Swanson, Jellinek & Malz (2005), concluded that it lacked utility as a taxonomically meaningful grouping.

 Extended the stratigraphic range of most taxa; many only previously known from Miocene strata or from locations outside the Otway Basin.

Palaeoenvironmental interpretation

 Suggested palaeoenvironmental interpretations based on assemblage compositions and foraminiferal data for all localities and bore-core horizons investigated. These were for latest Paleocene Pember Mudstone, the Early Oligocene Narrawaturk Formation and the Late Oligocene Gellibrand Marl at Heywood-10, and 16 Early Eocene Dilwyn Formation assemblages at Latrobe-1 and Rivernook.

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Palaeogeographic interpretation

 Identified the migration path of a Cytherella lineage that originated in the Late Cretaceous, Carnarvon Basin, and migrated and evolved to appear in the AAG by the Late Paleocene; it accords with the existence of a south-flowing current down the West Australian coast by at least the Late Paleocene.

 Identified a taxon common to both Australia and New Zealand, Glencoeleberis? thomsoni Hornibrook (1952) that is found in and above the latest Paleocene/earliest Eocene Pember Mudstone Member, in Early Eocene Rivernook Member, and in Late Paleocene/Early Eocene dredged marine sediments from Fiordland in the South Island, New Zealand, and used this as evidence of a latest Paleocene–earliest Eocene breach of the Tasmanian land-bridge.

Additional results

 Developed a technique for image enhancement of photographs of microscopic specimens taken through standard microscopes.

 Identified areas for future research:

 Re-sampling of key localities for selection of neotypes (if apparently lost material is not found), to increase specimen numbers enabling improved descriptions of low-number taxa in open nomenclature, and to provide more precise stratigraphic ranges.

 There are still 54 undescribed subsurface ostracod-bearing horizons that could not be covered in this study.

 Investigation of the soft anatomy of extant sinistral Cytherella.

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